Long-term temperature and precipitation records from the Falkland Islands

Transcription

1 INTERNATIONAL JOURNAL OF CLIMATOLOGY Int. J. Climatol. 35: (2015) Published online 27 May 201 in Wiley Online Library (wileyonlinelibrary.com) DOI: /joc.09 Long-term temperature and precipitation records from the Falkland Islands D. H. Lister a * and P. D. Jones a,b a Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, UK b Center of Excellence for Climate Change Research, Department of Meteorology, King Abdulaziz University, Jeddah, Saudi Arabia ABSTRACT: In this article, we develop long-term series of monthly average temperatures and precipitation totals for the modern recording site on the Falkland Islands (at Mount Pleasant Airport). The air temperature series extends back to 1895, but with 16 missing months in 1902 and 1907/8. The precipitation series extends back to 190, but has all but four months missing in the period All missing values during the early 1980s are infilled using the ERA-Interim Reanalysis. We compare long-term variations in both variables with the nearest long-term record from Punta Arenas in Chile, and for air temperature with a sea surface temperature series from around the islands. KEY WORDS climate series; temperature; precipitation; falkland islands; homogeneity Received 21 November 2013; Revised 21 March 201; Accepted 22 April Introduction The Falkland Islands has a fragmentary history of meteorological observations with the principal records being located in the Stanley region of East Falkland (Jones et al., 1999 for more detail about the early observations). In this region, observations of several meteorological elements began at Cape Pembroke Lighthouse (CPL) about 1850 and ended in 197 (Figure 1, Table 1). Brooks (1920) considered the record for temperature and sea-level pressure (the only two variables he studied) as being of better quality after the visit of the Scotia in 1903, even though Scott (1871) published monthly sea-level pressure averages for (Jones et al., 1999). Temperature records are only readily available since Observational recordings began in Stanley in 187 (Figure 1, Table 1; Brooks 1920), but were partly sporadic until More recently, all Falklands observations were disrupted by military actions between Britain and Argentina which began in April As a result of this dispute, Britain developed a modern airport at Mount Pleasant (Figure 1, Table 1), and a wide suite of meteorological observations are available for this site since July Temperature readings from Stanley are not available after This article discusses the development of long monthly climatic series of temperature and precipitation. The long precipitation series combines the Stanley and Mount Pleasant Airport (MPA) records and the long temperature series combines CPL, Stanley and MPA. Precipitation records are not available for CPL and not discussed by Brooks (1920), but they have been made at Stanley after * Correspondence to: D. H. Lister, Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, NR 7TJ, UK. d.lister@uea.ac.uk 61W CPL - Cape Pembroke Lighthouse St - Stanley MPA - Mount Pleasant Airport 60W East Falkland 59W MPA 58W 51S St CPL Figure 1. The observing locations on the Falkland Islands that have contributed to the long climate series of precipitation and temperature unlike temperature. All data apart from MPA have been adjusted to the observed climate at MPA, such that future measurements there can be simply added. To make the series as complete as possible, substitutions of missing values have been possible using Reanalysis from ERA-Interim (Dee et al., 2011), this applying to the few years beginning in 1982, when all observing was disrupted. 2. Temperature Although CPL began recording in 1850 (Scott, 1871), monthly average temperatures are only readily available from These values are given in World Weather 52S 201 Royal Meteorological Society

2 FALKLANDS CLIMATE SERIES 1225 Table 1. A summary of sources for the MPA-extended precipitation and temperature series includes Punta Arenas which is only used for comparison purposes. Observing location Providing source Overall period a Additional sources Cape Pembroke Lighthouse CRU Tmean archive RM (CPL, S, W, 21 m) Port Stanley (51.68 S, W, CRU Tmean archive UKFIT ; m) b precipitation Mount Pleasant Airport UKFIT temperature and From UKMO data (51.82 S, 58.7 W, 65 m) precipitation Punta Arenas (53.3 S, 70.9 W, CRU Tmean archive CRU ; WWR and UKFIT d 28 m) c precipitation archive Key to acronyms and notation used in Table 1 and elsewhere: CRU, Climatic Research Unit (for these sites the original source is WWR); RM, Réseau Mondial (Annual Publications from 1910 to 193); WWR, World Weather Records; UKFIT, United Kingdom Falkland Islands Trust; UKMO, UK Met. Office. a There may be missing blocks of data or individual values missing within the overall period. b Observing locations have moved around the Port Stanley area. c Observing locations have moved around the Punta Arenas area. d Punta Arenas is from CRUTEM with a few missing values inserted from the UKFIT series. It should be noted that the CRU T mean archive (CRUTEM) version of Punta Arenas had an adjustment made for a station move in 1963/ (Jones et al., 1986). Records, WWR (refer Jones et al., 2012 for details). Stanley observations are available in the Climatic Research Unit (CRU) archives and although starting in 187 they are fragmentary until The MPA observations have been supplied by the UK Falkland Islands Trust (UKFIT, refer to Table 1 for more details). The CPL data from WWR are in the CRU archives (for CRUTEM, refer The top panel of Figure 2 shows an initial plot of the three annual average temperature series (derived from the monthly time-series) that are the building blocks for the development of the extended MPA temperature series. For all the three locations (CPL, Stanley and MPA) we only have the monthly averages. In addition, the annual average value from the nearest grid box (refer Section re grid-boxes) to Stanley from ERA-Interim (Dee et al., 2011) is shown in the bottom panel. Initial observations indicate that both Stanley and CPL series are cooler than MPA, but the ERA-Interim series agrees well with MPA. In the next few paragraphs we discuss the sources of the various data series and the necessary adjustments for a near-complete record from The publication Réseau Mondial (RM, Meteorological Office, Air Ministry, London), during the period , provides two monthly mean temperature series for CPL calculated as the mean of six-four-hourly readings and also from (T max + T min )/2. These two series are important since WWR document a change in the method of calculation of monthly mean temperature at CPL during the period RM states that the daily mean (and hence the monthly mean) temperatures for CPL were calculated as the mean of six-four-hourly temperature readings for the period to 1930 and from then the mean of T max and T min was used. Why the change in the WWR source was made is not known, but the RM source enables the switch to be accounted for. Comparison of the WWR and both RM temperature series for CPL during their whole period of overlap allows some additional determinations to be made. First, there was close agreement when comparing the RM (T max + T min )/2 with the WWR/CRUTEM values during Annual-mean temperature deg. C Annual-mean temperature deg. C Stanley(unadjusted) and MPA ERA_Int 2mT Cape Pembroke(unadjusted) Falklands HadISST Stanley/CPL combined(thus adjustments) and MPA Figure 2. The top panel shows CPL (unadjusted), Stanley (unadjusted) and MPA annual-mean temperature series. While the Stanley series starts in 1923, the presence of a few missing monthly values, within the period , means that the annual time-series is only shown from The ERA-Interim mean temperature series is superimposed. The bottom panel shows CPL (adjusted for the change in the calculation of mean temperatures) and Stanley combined up to 1981 and MPA from the mid-1980s and the HadISST annual series for the seas around the Falklands. In the bottom panel the pre-1981 record from Stanley/CPL has not been adjusted to MPA. Annual values are based on all monthly values being available for each year. the period However, there were cases of large differences for two monthly values in 1932 (April and June). Inspection of these monthly values, in the context of their magnitude in preceding and following years, leads to the conclusion that the WWR (and hence CRU) values are incorrect. This is important for the calculation of the CPL to Stanley monthly conversion increments as in Table 2. Values from RM were therefore used as replacements. The close agreement also corroborates the information (from WWR), regarding the change in calculation method for T mean, for the period post It is essential, therefore, in the interests of homogeneity, that

3 1226 D. H. LISTER AND P. D. JONES Table 2. Monthly conversion adjustments used to produce a homogeneous T mean series for MPA using the data from CPL and Stanley. Standard deviations of the monthly differences, from which the average adjustments are calculated, are shown for those involving CPL. Month CPL: mean-of -six-four-hourly readings conversions to mean from (T max + T min )/2 ( C to be added) based on the period standard deviations given in brackets. The period at CPL adjusted is: CPL to Stanley conversion monthly increments to be added ( C) based on the period standard deviations in brackets. The period adjusted is: Stanley (extended by CPL) to MPA conversion monthly adjustments (from the net monthly differences between Stanley/HadISST and MPA/HadISST) ( C to be added) during the periods and The period adjusted is: a January 0.3 (0.25) 0.29 (0.66) 1.51 February 0.3 (0.17) 0.10 (0.58) 1.26 March 0.3 (0.35) 0.12 (0.5) 1.3 April 0. (0.21) 0.36 (0.7) 0.6 May 0. (0.21) 0.53 (0.6) 0.59 June 0. (0.27) 0.76 (0.0) 0.19 July 0. (0.17) 0.87 (0.39) 0.06 August 0. (0.2) 0.56 (0.5) 0.21 September 0.2 (0.18) 0.22 (0.6) 0.3 October 0.2 (0.13) 0.08 (0.8) 1.08 November 0.2 (0.17) 0.3 (0.50) 1.28 December 0.3 (0.19) 0.0 (0.69) 1.27 Annual mean a Our Stanley series contains 29 missing monthly values between 1982 and the pre-1931 subset of the CPL series should be switched to use the (T max + T min )/2 calculation. The presence of the parallel set of monthly values (via the different methods of mean monthly temperature calculation), during the period in RM, provides the means for this adjustment. The monthly adjustments, calculated to switch from the parallel T mean (based on six observations per day) series to that from (T max + T min )/2 are listed in Table 2. Adjusting the CPL series enables better comparison with the Stanley series back to Comparison for pre-197 shows a close relationship with the Stanley series, particularly before 1939 refer Figure 2. The correlation between CPL and Stanley annual mean temperatures during the period is somewhat low at 0.62, based on 16 years of overlap (but highly statistically significant with p = 0.02). The increase in values at CPL compared to Stanley after 1938 suggests a problem with one or both series. The most likely explanation for this phenomenon is that the problem lies with the CPL series. The annual-mean temperature series for CPL reaches almost 8 C (Figure 2, top panel) in 190 and 191 and these are unlikely in the context of the levels shown by Stanley but more importantly with those at Punta Arenas (see later in Figure 3). Given the doubts about the CPL series in the early 190s, the Stanley series seems more reliable. The extended-mpa series will use the Stanley series (where possible) from 1923 up to However, the presence of some missing monthly values in the WWR Stanley record (June 192, June to September 1925 and September 192) calls for remedial action if possible. The availability of the CPL record allows the missing monthly values to be filled, with the appropriate (CPL to Stanley) adjustment. Prior to 1923, the CPL series is used, adjusted to the (T max + T min )/2 method of calculating monthly averages. Monthly adjustment (CPL to Stanley) increments were calculated via the overlap differences between CPL and Stanley over the period For these adjustment values, refer Table 2. Some discussion of these adjustments will be made in the final section. The extended Stanley series shown in the bottom panel of Figure 2 reflects the final combination of the CPL and Stanley series after all adjustments. There are some gaps in the CPL series in the 1900s and there is little prospect of infilling these 16 missing months. The next step is to combine the MPA series with the extended Stanley series. There is a clear temperature difference between Stanley and MPA and the missing period in the early 1980s at both Stanley and MPA is also evident (Figure 2, bottom panel). MPA is clearly warmer than Stanley, despite being at a higher elevation (65 m; Table 1). In order to help infill the gap and adjust the levels we make use of data from two gridded sources: ERA-Interim and also estimates of sea surface temperature (SST) from HadISST (Hadley Centre Sea Ice and Sea Surface Temperature) data set for the seas around the islands (refer Dee et al., 2011 and isst/, Rayner et al., 2003, respectively). The close match between the ERA-Interim and MPA series offers the prospect of infilling values between the end of the Stanley and the start of the MPA series. The correlation when MPA and ERA-Interim annual mean temperatures are compared for the period is

4 FALKLANDS CLIMATE SERIES 1227 Annual-mean temperature deg.c Annual-mean temperature deg.c HadISST_ann_filtered MPA_extended_ann_filtered Punta Arenas_ann_filtered HadISST_annual MPA_extended_annual Punta Arenas_annual Figure 3. The top panel shows the annual T mean series for CPL/Stanley after adjustment to the MPA location and the substitution of missing values where this was possible. The HadISST annual series is also shown. In addition, the Punta Arenas annual T mean series is shown. The bottom panel shows the three series in the top panel after the application of a 10-year smoothing filter. Fifteen missing months in 1902 and 1907/8 have been replaced in the extended MPA series with the monthly averages to allow the smoothed series to be complete , based on 25 years with p < However, the very short overlap between Stanley and ERA-Interim (Figure 2) calls for an alternative means of relating the two series. ERA-Interim cannot be used as the linking series. The fact that ERA-Interim agrees well with MPA is understandable as it is likely that several meteorological variables (air temperatures and sea-level pressures, for example) measured at MPA have been assimilated at each of the four synoptic hours each day. For future ECMWF Reanalyses, it will be possible to asses this using the new observational feedback archive ( Figure 2 (bottom panel) shows the combined CPL/Stanley and MPA annual-mean temperature series and also plots the annual-mean SST series extracted from the gridded HadISST product. The series used is the mean of a five-by-five ( latitude/longitude) grid-box matrix centred on the Islands at 51.5 S and 58.5 W. Inspection of the plot shows a close relationship between HadISST and both Stanley and ERA-Interim particularly in the post-1960 period. The correlations for Stanley versus HadISST and MPA versus HadISST over the periods and are 0.37 based on a 22-year period (p = 0.09) and 0.0 based on the 25-year period, p = 0.05, respectively. Although, these correlations are low, the HadISST series can be used as the link between the Stanley and MPA series for the adjustment of Stanley to MPA. Monthly difference matrices were produced (HadISST minus Stanley and HadISST minus MPA). By subtracting these difference matrices, the monthly averaged values from the result become the monthly adjustments to apply to the CPL/Stanley series, to raise the level to that of MPA (Table 2) and the top panel of Figure 3. We have compared the two subsets of monthly differences over the two periods and , by the use of a t-test. With a probability value of <0.01, the two sets of differences with HadISST are shown to be from different statistical populations. The gap in the annual series plot (Figure 2) exaggerates the number of missing monthly values in the period as we required complete years to calculate the annual averages. The number of missing months in the temperature record is only 29 during the period that observations were affected as a result of the military conflict. The actual missing values for Stanley occur in March to December 1982, all months of 1983, January to May 198 and May and June The MPA and ERA-Interim series appear to agree very closely during the period (refer Figure 2 and the correlation statistics, above). The mean annual temperatures for both series (during the period ) are 6.6 and 6.5 C, respectively. However, on closer examination of the monthly differences between MPA and ERA-Interim during this period, some differences are apparent and these follow a seasonal pattern (Table 3). The ERA-Interim monthly values can, therefore, be used as substitute values for the 29 months but they require the appropriate monthly adjustments. The fact that the nearest ERA-Interim grid-box is a marine box situated to the south of MPA helps to explain the seasonal differences and the need to adjust for them. Refer to Section for more on this. The nearest land grid box to the Falklands for ERA-Interim is on the South American mainland. The top panel of Figure 3 shows the effects of the adjustments to the Stanley series in the MPA-extended series which is now totally complete from 1909 to the present time. The lower panel of Figure 3 will be described in Section later. The MPA-extended temperature series has, in the absence of the availability of long and homogeneous temperature records within a reasonable radius, been subjected to homogeneity assessment using RH-TEST ( Wang, 2008). This test identifies potential break-points via the use of internal statistical properties. The test reveals no homogeneity problems with the MPA-extended temperature series. 3. Precipitation Input data for monthly precipitation totals have come from a Stanley series provided by UKFIT covering the period (Figure 1, Table 1). This series had a mostly missing block of data for the period and had some missing values which were coded as zero during the 1920s. In addition, there were some missing values during the period February 1982 to December 1992, partly due to the military action. After attempts to locate further data for the latter missing period, some additional data were found through the involvement of Manfred Keenleyside of the Falkland Islands Government (personal communication).

5 1228 D. H. LISTER AND P. D. JONES Table 3. Monthly temperatures and temperature differences during the period ERA-Interim and MPA Period Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann ERA_Interim, C MPA-obs, C ERA minus MPA, C Annual precip(mm) UKFIT Stanley annual precipitation UKFIT MPA annual precipitation Annual precip(mm) UKFIT Stanley annual precipitation UKFIT MPA annual precipitation ERA-Int annual precipitation Annual precip(mm) MPA_Stanley (extended/infilled and pre-196 adjusted) annual precipitation plus smoothed Punta Arenas annual precipitation plus smoothed Figure. Top panel shows annual total precipitation (mm) for both Stanley and MPA. The middle panel shows the same as the top panel and also includes the ERA-Interim annual precipitation totals for The bottom panel shows the final MPA-extended series after the adjustment of the Stanley subset to MPA and the infilling of missing monthly values during the period 1982/83 (using ERA-Interim adjusted values) and the homogeneity adjustment to the pre-196 subset. In addition, the Punta Arenas annual precipitation series and its 10-year smoothed values are shown. In contrast to temperature, monthly precipitation recording at Stanley continued after An MPA record, as provided by UKFIT, starts in July 1986 and is continuous to the present time. This means that when the Stanley and MPA records were combined, there were 23 missing months within the period , slightly fewer than for the average temperatures. There are no other records from the Islands at this time that could be used to fill gaps in the series. Figure (top panel) shows the Stanley and MPA precipitation series before their combination. The ratio of the annual catch at the two sites during their period of overlap has been calculated to enable one to be converted to the other. The Stanley record was not quite complete, even after the Keenleyside additions, and the years 1986, 1987 and 1992 could not produce annual totals (as some months were missing) towards the calculation of the catch ratios. The average ratio (MPA/Stanley) of the annual totals is based on the years and When this relationship is disaggregated further by the comparison of seasonal, as opposed to annual catch ratios, the result is remarkably similar for all four 3-month seasons. The seasonal ratios are given in Table. The consistency shown between the seasons allows us to use the annual-totals ratio to perform the Stanley to MPA adjustment. The number is less than unity indicating that MPA receives slightly less rain on average than Stanley. All available MPA values have been used and all non-overlap

6 FALKLANDS CLIMATE SERIES 1229 Table. Seasonal-precipitation (MPA/Stanley) catch ratios during the period MAM JJA SON DJF Stanley values have been multiplied by the annual-ratio factor. The same factor was used for all months of the year. In the interests of having the MPA-extended precipitation series as complete as possible, and in the absence of alternative station records from which missing values could be estimated, the missing 23 values (during 1982 and 1983) have been estimated using ERA-Interim reanalysis precipitation values (see earlier links to ERA-Interim reanalysis products). The closeness of the fit between the ERA-Interim precipitation and the MPA series can be seen in Figure (middle panel), which shows the annual total precipitation from all three series. The correlation between Stanley and ERA-Interim annual precipitation is 0.5, based on the 25 pairs of annual totals (without missing values) between the years 1979 and 2010 (p = 0.005). The correlation between MPA and ERA annual precipitation is also 0.5 based on the 25-year period, (p = 0.005). However, before going ahead with any substitution of missing values, we further disaggregate these relationships (based on annual totals), between the Stanley and ERA-Interim and also MPA and ERA-Interim series. This has been undertaken by the correlation of all non-missing monthly values from each standard season, between the Stanley and the MPA series and ERA over the same periods as the annual analyses. The seasonal correlation values are also shown in Table 5. While somewhat lower than the annual-total correlations, the seasonal approach is still producing statistically significant results. This allows us to go ahead with the use of ERA monthly precipitation totals to infill the missing values in the years 1982 and The adjustment factor (calculated from the ratio of overlap annual totals) is Missing monthly values were thus estimated and inserted into the MPA extended series. Before the final acceptance of the MPA-extended series, and in similar circumstances (no relatively close neighbours) to the MPA-extended temperature series, we have used RH-Test to assess the homogeneity of the long precipitation series. In this case, the test shows a break-point in 195. Following this date, the step-jump is to lower rainfall. This concurs with information regarding a site change in 195 (Pepper, 195). The new site, as of September 195, is reported to be over exposed with regard to the rain gauge location, with a likely consequence of undercatch. In contrast, the previous location was sheltered but likely prone to sea spray which could enter the rain gauge in strong northerly winds. Given this strong corroboration for the break-point, the final precipitation series has been adjusted accordingly. The average value for the pre-196 adjustment ratio is 0.79 (with respect to the MPA-extended series as in the middle panel of Figure ). Figure (bottom panel) shows the final MPA-extended series (as annual precipitation totals). There appears to be little prospect of locating any of the missing Stanley monthly precipitation totals for the period Figure (bottom panel) also shows the annual precipitation series for Punta Arenas and this will be discussed in the next section.. Discussion and conclusions The linear trend for the MPA-extended temperature series during the period is 0.5 C/century and this is highly statistically significant (p = 0.002). While the warming trend is evident, a period of relatively high temperatures (Figure 3), centred on 193, is worthy of special attention. The bottom panel of Figure 3 shows the decadally-smoothed temperature series for MPA-extended, and indicates the highest levels of temperature during the early 190s. This is also reflected in the series for Punta Arenas, though not to quite the same extent. This period has been identified by others as being anomalously warm for comparable regions in southern South America. Schneider and Steig (2008), working with Antarctic Peninsula ice cores, identify an anomalously warm decade ( ), which they attribute in part to the major El Nino event. Punta Arenas is the nearest long-term station to MPA. Series from Argentina are closer, but they either start later or contain many missing values. The MPA-extended temperature series generally follows that of Punta Arenas very closely on a year-to-year basis, particularly since This can be seen in the top panel of Figure 3. The extremely cool period before 1915 at Punta Arenas can only be compared with MPA if the missing values in the MPA-extended record, during parts of 1902 and 1907/08 (16 months in total), are estimated by the use of MPA monthly average temperatures for the contemporary period ( ). The bottom panel of Figure 3 shows that the cool period recorded at this time at Punta Arenas may not have been experienced in East Falkland. This casts some doubt on the severity of the Punta Arenas cold period. The period is relatively short however, as temperatures from 1895 to about 190 are near the long-term average for Punta Arenas. The correlation between the two annual-mean temperature series, during the 101-year period is (p < 0.001). The close relationship between the Punta Arenas and MPA-extended series suggests that the main controlling influence on the temperature of both stations is the westerly atmospheric/oceanic circulation and SSTs. The climate of the Falkland Islands is influenced by the Andes to the west, surrounding waters and the Antarctic Peninsula to the south (Turner and Pendlebury, 2000). While Punta Arenas is somewhat further south than MPA (Table 1), the similarity in the variability of their respective temperature records is close. Both Punta Arenas and the Falkland Islands come under the influence of the cold waters of the Antarctic Circumpolar Current (otherwise

7 1230 D. H. LISTER AND P. D. JONES Table 5. Seasonal correlations between the Stanley and ERA-Interim precipitation series ( ) and also the MPA and ERA_Interim precipitation series ( ). Correlation pair Period Season (3-month) Correlation r n-values (monthly) STA/ERA MAM STA/ERA JJA STA/ERA SON STA/ERA DJF MPA/ERA MAM MPA/ERA JJA MPA/ERA SON MPA/ERA DJF ΔP hpa ΔP hpa ΔP hpa ΔP hpa r= 0.0 MAM r= 0.0 JJA r= 0.39 SON r= 0.6 DJF Tanoms(deg.C) Tanoms(deg.C) Tanoms(deg.C) Tanoms(deg.C) Figure 5. Seasonal averages of monthly pressure differences (MPA minus Punta Arenas, left axes) and seasonal averages of monthly temperature anomalies (right axes) at MPA. known as the West Wind Drift). In the case of the Falkland Islands, a northerly offshoot of the Antarctic Circumpolar Current (the Malvinas or Falkland Current) feeds cold waters around the Islands. When the MPA-extended and Punta Arenas precipitation series are correlated [using the same period , but with omitted, as for temperature (Figure 3)], the correlation is statistically not significant (refer also the bottom panel of Figure ). To examine further the close relationship between the fluctuations in temperature at Punta Arenas and MPA, we use monthly pressure differences between the two sites and seasonal temperature anomalies. The seasonal pressure differences (MPA minus Punta Arenas) have been compared with temperature anomalies at MPA for each season. The results of this exercise can be seen in Figure 5. For all four seasons, the correlations are statistically significant indicating that MPA temperature is responding to circulation features in the region. Warmer temperatures at MPA relate to more northerly air circulation as expected. Correlations between the same pressure differences and

8 FALKLANDS CLIMATE SERIES 1231 Table 3. Air temperatures over the ocean are less sensitive than those over land. Near land-surface air temperatures tend to be more responsive to radiation gains or losses than those over the sea. Winter maritime temperatures are generally higher than those over land and the opposite is the case in summer. All the monthly temperature and precipitation data used in this study and the resulting MPA-extended series will be available from the CRU web site ( uea.ac.uk). Figure 6. Monthly increments (from Table 2 due to local geographic effects) that have to be added to the Stanley temperature series to adjust them to the temperatures at CPL and MPA. In the MPA-extended series, the differences between Stanley and CPL were used to adjust CPL to Stanley. Punta Arenas temperature (not shown) are much weaker and mostly not statistically significant. The pressure gradient is much more relevant to MPA rather than Punta Arenas but this analysis shows that both temperature series respond to the same circulation features. On a more micro-climatic note, we note that there are some subtle differences in monthly/seasonal temperature characteristics when looking at the series that make up the MPA-extended series, that is, MPA, Stanley and CPL. All three stations come from a relatively small part of East Falkland and all three are close or relatively close to the southerly-facing coast (Figures 1 and 5, Table 1). MPA is ca. 50 km south west of Stanley and CPL. Stanley is cooler than CPL on an annual basis (Figure 2, Table 2) by approximately 0.2 C (Figure 6). However, this is mostly seen in the winter months and is offset by higher temperatures at Stanley in the summer months of January and February. This will be the result of CPL being more exposed at the coast where the extremes of temperature are moderated by exposure to winds directly off the sea. The annual temperature at MPA is higher than that at Stanley (Figures 2 and 6, Table 2), by about 0.8 C. In contrast to the differences between CPL and Stanley, the smallest (absolute) differences occur in the winter months of June and July. The relative warmth at MPA occurs in all but the winter months. MPA is the farthest of all three stations from the coast (approximately 12 km) and it seems that the damping of cold winter extremes at Stanley, due to its more coastal location are outweighed by the tendency for warmer extremes at MPA during the non-winter months. In addition, the weather at MPA is affected by the close proximity of the Wickham Heights (Turner and Pendlebury, 2000), an area of high elevation (generally over 300 m) situated some 7 km to the northwest. Finally, we examined seasonal temperature relationships between MPA and ERA-Interim. As already mentioned, the nearest (to MPA) ERA grid-box is marine and not a land box. The monthly/seasonal differences are evident in Acknowledgements This work has been supported by the UK Falklands Islands Trust (UKFIT). We thank the support of UKFIT and in addition Manfred Keenleyside, Owen Summers and Jim McAdam. We also thank Nicolas Butorovic of the Institute of Patagonia, University of Magallanes, Punta Arenas for his help with data provision for Punta Arenas. References Brooks CEP The climate and weather of the Falkland Islands and South Georgia. 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