ANALYSIS OF CLIMATIC CHANGES IN THE SAN JUAN MOUNTAIN (SJM) REGION DURING THE 20 TH CENTURY. Imtiaz Rangwala

Transcription

1 ANALYSIS OF CLIMATIC CHANGES IN THE SAN JUAN MOUNTAIN (SJM) REGION DURING THE 20 TH CENTURY Imtiaz Rangwala MTNCLIM

2 Objectives (as proposed) Nature of climate change in the SJM It s relationship to changes in the stream flow in the region To explore the mountains 2

3 3

4 Kendall in the Wind[ow] 4

5 Overview Historical climate records for the SJM region Analysis of these records for the 20 th century - Temperature - Elevation Dependent Warming? (NWS vs SNOTEL) - Precipitation, SWE, Snowdepth Role of the Pacific Climate 5

6 Study Region COLORADO SJM 13 Counties W and N 6

7 Data Mining Monthly Avg. Temperature: NWS: (26), SNOTEL (bigger (23) dataset since 1949) Precipitation: SNOTEL: NWS (22), started SNOTEL early (26) 1980s Snow water equivalent (SWE): SNOTEL (26), Since mid-1940s Snow Course (26) Snow-depth: Snow Course (26) JAN thru JUN Since mid-1940s and refining (esp. SNOTEL data) discarding impossible values filling in missing values 7

8 Temperature 8

9 Possible 2 o C warming between Rapid warming between 1995 and 2005 Both NWS and SNOTEL sites confirm this trend NWS anomalies relative to SNOTEL anomalies relative to NWS vs SNOTEL r =

10 r =

11 SJM warming in context to warming elsewhere 11

12 CO division - 2 Div. 2 12

13 ? r =

14 NASA/GISS 14

15 At SJM: Surface warming twice that of global average Mid century cooling occurred later Late century warming started later too but happened more rapidly r =

16 r =

17 Recent Decades 17

18 Trends based on the 5 o x 5 o gridded GHCN (Global Historical Climatology Network) land surface dataset provided by NCDC, NOAA 18

19 SJM: NWS vs SNOTEL SNOTEL sites 2500 ft higher than NWS sites Warming larger at SNOTEL than NWS except winter Spring and summer: Warming at least 2 times higher at SNOTEL Similar increases in T-max and T-min 19

20 Warming rates for 3 decades (C/decade) Large warming in SNOTEL > NWS Similar increases in Max. T and Min. T during particularly at SNOTEL sites 20

21 Warming rates for 3 decades (C/decade): Seasons : The decade of highest warming? Warming in all seasons at both sites Higher at SNOTEL except winter Very large during spring and summer at SNOTEL 21

22 Conclusions:Temperature The surface temperature in the SJM region may have increased by about 2 o C between Half of this warming happened between ; which is confirmed at both NWS and SNOTEL sites Temperature trends correlate well between NWS and SNOTEL sites More recent trends in warming in the San Juans appear to have started later than most other regions in the U.S. but has been more rapid 22

23 Broad temperature trend in the SJM is to similar to that of the contiguous US for the 20 th century Elevation dependency in local warming higher rates at SNOTEL sites 23

24 Snow 24

25 (Nov-May) Anomalies are normalized 25% decrease during NWS vs SNOTEL r =

26 Snowfall And Snow-depth r = % decrease in snow-depth during

27 Snowfall And SWE 40% decrease in SWE during Decrease in the total annual snow residence time Snowfall vs SWE: r = 0.83 SWE (Snow Course vs SNOTEL): r =

28 Snowfall And Snow-depth Decadal Average Snowdepth following snowfall trend 28

29 Snow-depth: Snow Course Sites Large snowdepth decreases in mid-late spring 29

30 Increase in Spring Melt? 30

31 Pacific climate indicies and the SJM climate 31

32 I-80 32

33 (+) ENSO and (+) PDO More Snowfall and Lower Winter Temperatures in the SJM 33

34 Pre-1975: Relationship exist but weak Post-1975: Breaks down; in fact becomes opposite? 34

35 Conclusions: Snow Rapid decreases in Snowfall (25%), SWE (40%) and Snowdepth (25%) at SNOTEL/Snow Course sites during the period. These decreases in Snowfall cannot be explained by the traditional ENSO/PDO pattern. Large warming in spring and early summer can be related to the decreases in snow amount through the snow-albedo feedback mechanism Large decreases in SWE in spring may reflect in significant changes in the seasonal streamflow in the region. 35

36 Acknowledgements MSI mini-grant program Koren Nydick Jim Miller and Dave Robinson Rutgers Staff and Researchers at MSI People of Silverton DATA Sources 36

37 Thanks!!! 37

38 Is there a relationship? Rapid temperature increases And A rapid snow loss (In recent decades) 38

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42 r =

43 r =

44 Monsoon Precipitation No long term trends NWS vs SNOTEL r = 0.91 However, a sharp decrease between