Enhancing swimming pool management decisions with climate information

Transcription

1 Meteorol. Appl. 9, (2002) DOI: /S Enhancing swimming pool management decisions with climate information David Changnon, Jesse Sparks, Andrew Burgoyne and Chad Hahn, Meteorology Program, Department of Geography, Northern Illinois University, DeKalb, IL 60115, USA Ross Seymour, Swimming Pool Management Systems, Inc., Woodridge, IL 60517, USA Historical climate conditions were examined to determine whether climate information could improve decisions concerning the seasonal maintenance and operations of regional outdoor swimming pools in heavily urbanised northeastern Illinois. Key weather-sensitive issues defined for pool companies concern time periods for maintenance (including pool painting), weather limits to pools being open, and hot days which extend hours of pool operation. The specific conditions included the frequency of spring and fall painting periods (defined as dry conditions for two or more days with Tmax >18 C (65 F) and Tmin > 4 C (40 F)); summer inclement weather days (days with precipitation > 2.54 mm (0.10 inch) with not more than 2 consecutive hours of dry conditions during open swimming hours and/or Tmax < 21 C (70 F)); and hot days (Tmax > 32 C (90 F)) were examined. Climatic records for the region going back 42 years revealed that there were nearly twice as many fall painting periods as those in the spring, indicating that greater emphasis should be placed on pool painting after the swimming season. The average number of inclement weather days was more than twice the number the company budgeted for at the beginning of each swimming season. Plans to extend swimming hours on hot days involves a risky decision since the number of hot days varies dramatically from year-to-year in the Chicago region. Studies showed that winter negative sea-surface temperature anomalies in the central Pacific were related to an above average number of spring painting periods. Also, a higher number of hot summer days occur following El Niño-classified winters. Results reveal that decision-makers in the swimming pool management industry can improve several management decisions by including climate information. 1. Introduction and background The outdoor recreation industry is directly affected by weather conditions; however, the use of climate information (which can describe the frequency and duration of limiting conditions) in important planning decisions is generally not well understood either by many atmospheric scientists or by decision-makers in the affected sectors. The recreation business is dependent on actions by individual participants, and their involvement usually depends on favourable weather conditions (Thompson and Perry 1997). According to the International Society of Biometeorology, relatively little research has been undertaken in recreation and tourism climatology, and the lack of information has led to a wide misconception that climate conditions are constant and normal. Since the weather that combines to create climate is non-fixed, it is important to investigate past and present data to improve climate-sensitive decisions by the recreation industry. Research that could help the swimming pool industry includes delineation of the climate factors important to open-air swimming pools. This allows industry decision-makers to predict seasonal swimmer numbers, staffing needs, and opportunities to complete maintenance activities outside of the swimming season. Swimming pools frequently become an icon of energetic recreation in the lazy days of summer in many climate zones. It is those long and hot summer days that help make money for swimming pool businesses. Memorial Day weekend (last weekend, including Monday, in May) through Labor Day (first weekend in September) typically marks the beginning and end of the summer swimming pool season in the mid-latitude climates of the USA. Pools use this period of approximately 100 days to maximise their business potential. During this time, swimming pool managers must meet the demands of the industry and its patrons. This includes keepingthe pools safe and injury free, providing competent decisions to run the facility, and providing the patrons with a clean, well-maintained environment. Smaller pool facilities with fewer clients find it hard to meet these three industry standards. In order to compete successfully with larger pools, owners frequently seek assistance from swimming pool management com-panies. Such companies provide the necessary services including staffing and payroll, maintenance and service availability, and pool 461

2 David Changnon, Jesse Sparks, Andrew Burgoyne, Chad Hahn and Ross Seymour safety. The largest number of pool management companies exist along the east coast and southern regions of the United States. Some of the larger companies manage over 300 pool properties and some 1,000 lifeguards, though not all management companies have this type of volume or location. Swimming Pool Management Systems (SPMS) in Woodridge, Illinois, while not comparable in size to some of the larger companies, has provided its services to over 400 commercial swimming pools since 1983 in the Chicago metropolitan area. Currently, SPMS has individual contracts with 40 commercial swimming pool facilities, and offers coverage options that include, but are not limited to, providing staff and payroll coverage, opening and closing facilities each season, repair and maintenance capabilities, and sandblasting and painting. In an effort to maximise profits and/or reduce losses associated with each contract, the manager of the company has sought to increase his understanding of how climate influences both seasonal maintenance and operational activities throughout the year. This paper addresses the project carried out with this pool manager. The first task was to define the weather-sensitive activities and levels of conditions that were critical. At SPMS, some 25 to 35 pools are painted during a typical spring season. The painting jobs are restricted to the dates between 1 April and the start of the Memorial Day weekend in late May, which marks the start of the swimming season. This period is often characterised by warmth sufficient for successful painting. The key to painting is to identify dry periods long enough for the painting jobs to be completed. Small painting projects require two days and larger pool projects require three days of warm and dry weather. The manager of SPMS identified a simple threshold to define satisfactory painting periods: daily minimum temperature (Tmin) > 4 C, daily maximum temperature (Tmax) > 18 C, and no precipitation for at least two consecutive days. After further discussions, the SPMS manager requested that fall also be considered for pool painting. The period from 8 September to 25 October (last day with an average Tmax of 18 C) was examined to determine the number of potential painting periods and how these differed from those in spring. 462 Two other weather-related issues arise during the swimming season: first, the number of inclement weather days, and second, the number of hot days with Tmax > 32 C. Inclement weather days were defined by the manager as: days in which the pools are closed due to wet conditions (daily precipitation > 2.54 mm and not more than two consecutive hours of dry conditions during open swimming hours), and/or days closed due to cool conditions (T < 21 C for any hour without precipitation). A decision to not open the pool on a given day is generally made by the pool manager in the late morning, prior to noon, and is based on current and projected weather conditions. An example of inclement weather conditions would be steady and continuing rain with a noon-time temperature of 18 C. In northeastern Illinois these weather conditions occur most frequently at the beginning (late May through mid June) and end (late August through early September) of the swimming season and are often associated with the passage of extra-tropical cyclones. Although it appears that weather forecasting could play a role in this operational activity, decisions to close pools are made by the pool manager based on whether he/she believes that current conditions will continue through a good part of the day (resulting in low attendance) and thus meet the stated criteria. Characterising the inclement weather day climatology of the region would help the pool decision-makers in negotiating annual contracts for the swimming pools they manage since the contract accounts for a pre-determined number of inclement weather days that may occur. This is important because SPMS is not required to pay its workers on those days, and funds are held back to compensate for lost labour. At the present time, the contracts allow for five inclement weather days per summer; however, it is clearly in SPMS s interests to establish whether this number is appropriate for future contracts. Understanding the climatology of hot days (days with Tmax > 32 C) represents a different management issue as pool owners would want to extend hours on those days. The decision to extend the hours would be made by the pool manager and be based on whether late afternoon (approximately 3 pm) air temperatures were > 32 C. Such an extension in pool hours would require SPMS to pay their employees for the extra hours worked. Furthermore, more pool chemicals would need to be purchased to handle the greater pool use. Climate records were used to assess the frequency distributions of the three weather-sensitive activities. Seasurface temperature anomalies (SSTA) in two areas of the Pacific Ocean were examined to determine whether these sensitive weather events could be forecasted a season in advance. Ocean temperature anomalies in the tropical and central Pacific Ocean affect global circulation patterns, which adversely affect weather patterns in many areas of the world. The El Niño/Southern Oscillation (ENSO) phenomenon explains climate variability (seasonal temperature and precipitation anomalies), and subsequently is frequently used for long-lead seasonal forecasts (Barnett et al. 1999). The Pacific/North American (PNA) pattern manifests itself in the north and central Pacific and is one of the most prominent modes of low-frequency variability in the northern hemisphere extra-tropics (Bell 1997). Although these indices have been associated with seasonal climate anomalies in the United States, this study will examine whether there is any relationship to specific weather events.

3 Swimming pool management decisions The two objectives of this project were 1. to provide SPMS with climate information based on determining the inter-annual variability of the previously mentioned spring and summer events, and 2. to develop decision models by relating the number of painting periods, inclement weather days, and hot days each year to previous winter (December March) SSTA in the central and tropical Pacific Ocean regions. If a relationship exists between the average frequency of the weather-sensitive events and a coupled oceanic/ atmospheric index, pre-season decisions can be improved and may result in increased profits and/or reduced operational losses. 2. Data and analytical methods Daily precipitation and temperature (Tmax and Tmin) data for Chicago O Hare International Airport were obtained for the period (1959 being the first year with complete weather data) from the Midwestern Regional Climate Center (MRCC). This station was selected for two reasons: first, both hourly and daily climate data were available for analysis, and secondly, the data collected at O Hare represents the official data for the Chicago area and the SPMS manager could justify its use in contract negotiations with pool owners in the Chicago metropolitan region. The daily data were analysed to determine the number of painting periods during each spring (1 April 23 May) and fall (8 September 25 October), and the number of inclement weather days and hot days in summer (23 May 7 September). Having identified summer days with precipitation > 2.54 mm, it was essential to investigate the allied hourly precipitation and temperature data to determine whether two or more consecutive precipitation-free hours with temperatures higher than 21 C occurred so that the pools could be opened. For example, a day in which 50 mm of precipitation fell at O Hare does not necessarily merit inclement weather day status, since it is possible that the rain won t fall during the entire extent of normal pool operating hours ( hrs). Hourly precipitation and temperature data for O Hare were analysed to determine the number of inclement weather days. The available hourly data encompassed the period, which limited analysis of the inclement weather days to that 37-year period. An understanding of the climatological statistics associated with each seasonal weather event was imperative to optimise SPMS management decisions. Hence the mean, standard deviation, coefficient of variation, annual time series, and 5-year running means were determined (based on the period of data available) so that the SPMS manager could objectively determine the appropriate climate-sensitive planning strategies before each season. The SPMS manager expressed heightened interest in using climate information derived from the most recent years when negotiating the annual contract with pool owners. According to Lamb and Changnon (1981), the previous five years constitute the best averaging period to predict next year s seasonal weather conditions in Illinois. This forecast, which is essentially a persistence forecast, always emphasises the last five years. The 5-year mean and standard deviation were computed for each weather event and were compared with the period-of-record values. As input to the decision (predictive) models, SSTA data were obtained for the tropical and central regions of the Pacific Ocean. Annual classifications of winter (December March) ENSO states were based on a method described in Trenberth (1997) and Changnon et al. (1999). A visual and statistical association between the classified ENSO years and the total number of painting periods per spring and fall was completed to determine if any relationship existed. A student t-test was used to determine whether there were statistically significant differences between the total number of painting periods in El Niño, La Niña, and neutral ENSO years. Similar analyses were completed for inclement weather days and hot days. SSTA in the central Pacific Ocean, which are associated with the PNA pattern, were examined. Data from the NCEP/NCAR reanalysis were used to produce estimates of SSTA in the central Pacific Ocean. The reanalysis used a frozen state-of-the-art global data assimilation system and a database as complete as possible to eliminate perceived climate jumps and discontinuities associated with analysis procedure changes. These data were obtained from the National Oceanographic and Atmospheric Administration (NOAA) web site. Kalnay et al. (1996) reviewed these data and indicated that they could be confidently used for research. SSTA graphs were constructed for the winter months (December March) prior to the spring/ summer seasons. A winter average anomaly pattern was then developed. The winter anomalies were compared to the number of painting periods, inclement weather days, and hot days. Similar to the analysis completed for the ENSO anomalies, a student t-test of means was performed to determine the statistical significance of any relationship found. 3. Results 3.1 Spring painting periods The 42-year climatology of spring painting periods is shown in Table 1. The mean is nearly seven painting periods each year during the spring. This number varies 463

4 David Changnon, Jesse Sparks, Andrew Burgoyne, Chad Hahn and Ross Seymour tremendously on a year-to-year basis (standard deviation of 4 and coefficient of variation of 0.59), with annual values ranging from 0 to 14 (Figure 1). The smoothed values (based on the five-year running mean) indicated that multi-year periods of increasing and decreasing trends have occurred since The most recent five-year period has seen a smaller number of painting periods (5.2), as shown in Table 2, than the long-term average (6.8). Table 1. Climatological information (annual mean, standard deviation, and coefficient of variation) for spring and fall painting periods ( ), inclement weather days ( ), and hot days ( ). Event Annual Standard Coefficient mean deviation of variation Spring painting periods Fall painting periods Inclement weather days Hot days Results of a t-test indicated that a statistically significant difference (at the 90% level) in the number of spring painting periods existed when comparing positive and negative central Pacific SSTAs years. The average total number of painting periods during positive (warm) central Pacific SSTA was higher (8) than that of negative (cool) SSTA years (6.5). Table 2. Most recent 5-year mean and standard deviation for spring and fall painting periods ( ), inclement weather days ( ), and hot days ( ). Event 5-Year 5-Year Standard mean deviation Spring painting periods Fall painting periods Inclement weather days Hot days Because the average number of spring painting periods was considered low, and quite variable from year-toyear, the SPMS manager asked if the fall season might be a better time to complete some of the pool painting. The average number of dry days that occurred from 8 September to 25 October in the 42-year period is ten (Table 1) i.e. three more than expected in spring. When considering the past five years (Table 2) the average number of painting periods increased to 12.4, more than double the average number of spring days during the same period. Furthermore, the inter-annual variability is less in fall than spring (Figure 2), with a lower coefficient of variation (Table 1). With a higher average number of painting periods and lower variability, the fall season appears to be a more optimal time of the year for SPMS to focus on its pool painting. However, no relationship between Pacific Ocean SSTA and fall painting periods was found # of Painting Periods Annual Values Running Mean Year Figure 1. Annual number and 5-year running mean (centered on middle year) of spring painting periods for the period

5 Swimming pool management decisions # of Painting Periods Annual values Running mean Year Figure 2. Annual number and 5-year running mean (centered on middle year) of fall painting periods for the period Inclement weather days Analysis of hourly and daily temperature and precipitation data for O Hare revealed an average of 11.3 inclement weather days per swimming season (Table 1) during the 37-yr data period ( ). Over the most recent five years (Table 2) the average number of inclement weather days increased to 14. The long-term variability in the number of inclement weather days is much less than that for painting days (Figure 3) with a standard deviation of 4.5 and a coefficient of variation of Since the mid-1970s there appears to have been a general increase in the number of inclement weather days. As previously mentioned, SPMS budgets its pool contracts each year on the basis of only five inclement weather days, more than 50% less than the average determined in this study. In fact, during the 37-yr period, there were five or less inclement weather days in only three of those years. Fifteen or more inclement weather days occurred in ten of the 37 years. This analysis indicated that it is important for SPMS to contract for the occurrence of a higher number of inclement weather days prior to the beginning of the swimming season. No relationship between the number of summer inclement weather days and SSTAs in the tropical and central Pacific was found. 3.3 Summer hot days An average of approximately 15 hot days per summer season occurred during the 42-year period (Table 1). Over the most recent five years the average has dropped to 11.6 hot days per summer (Table 2). The annual variability of hot days was very large with a standard deviation of 9.8, a coefficient of variation of 0.64, and values that range from 3 to 46 (Figure 4). There was some relationship between the number of hot days and the previous winter SSTA in the tropical Pacific. A t-test analysis revealed that statistically significant differences (at the 90% level) exist in the mean number of hot days in El Niño years (21.3) versus La Niña years (13.9). This result indicates that in the summer following an El Niño winter SPMS should expect a higher number of hot days, a condition which may cause the SPMS manager to sign on more lifeguard staffs and to plan for above average use of pool chemicals. 4. Conclusions Daily weather has a direct impact on recreation industries, especially open-air swimming pools. A regional swimming pool management company in the Chicago metropolitan region wanted to know whether an increased understanding of climate could enhance its seasonal maintenance and operational decisions. Three pool-related issues were examined: off-season pool painting, number of inclement weather days and hot days in the swimming season. Decisions related to each of these issues had important economic consequences for the company and thus integrating climate information into these decisions was viewed as a way to potentially increase profits. Furthermore, the company 465

6 David Changnon, Jesse Sparks, Andrew Burgoyne, Chad Hahn and Ross Seymour # of Days 15 Annual Values Running Mean Year Figure 3. Annual number and 5-year running mean (centered on middle year) of summer inclement weather days for the period # of Hot Days Annual Values Running Mean Year Figure 4. Annual number and 5-year running mean (centered on middle year) of summer hot days for the period manager wanted to know if decision-making (predictive) models existed that could provide guidance with decisions a season or two ahead. Through discussions with the company manager, weather thresholds were determined for the three issues described above. Then, using hourly and daily precipitation and temperature data spanning 42 years ( ) observed at Chicago O Hare Airport, descriptive climatologies were developed for off-season painting periods, summer (Memorial Day weekend through Labor Day) inclement weather days and hot days. Interestingly, this basic climate information indicated that the swimming pool maintenance com- 466

7 Swimming pool management decisions pany could enhance its operations and profits by making a few changes. In the past the swimming pool maintenance company has scheduled the vast majority of pool painting projects for spring. However, on average there were three more painting periods in the fall than in spring, and with less inter-annual variability in the fall the swimming pool maintenance company should move the majority of its painting from spring to fall. Shifting the pool painting emphasis to fall has two primary benefits for the company: (1) reduced economic losses associated with the hiring and scheduling of seasonal painters and purchasing and maintaining painting materials and equipment, and (2) implementation of improved long-term painting strategies because analyses indicate a more consistent number of pools can be painted in the fall. Currently, the annual contracts that the management company signs with pool owners only allow for five inclement weather days each swimming season. As of 2001, each inclement weather day beyond what is covered by the contract costs the company $5,200. An evaluation of climate data using the threshold defined by the company manager indicated that, on average, more than twice that number of days (11.3) occur each swimming season. Given the lower inter-annual variability associated with these days it seems appropriate for the management company to increase the number of inclement days in its contract and potentially save $25,000 or more a year. To further improve inclement weather day (pool-closing) decisions, the swimming pool management company may want to consider the potential benefit from using enhanced or value-added short-term weather forecasts, produced by private sector meteorologists, in these decisions. As pool owners express a desire to extend pool opening hours on hot days, the swimming pool management company must consider the added costs associated with added labour (lifeguards) and maintenance (chemicals). On average, the Chicago region experiences approximately 15 hot days a year; however, owing to the large inter-annual variability (range from 3 to 46 days during the 42-year period) these costs could vary dramatically from year to year and thus it may be unwise for the company manager to use a set number of hot days in the annual contract negotiations with pool owners. Since relationships between Pacific Ocean SSTAs and pool-related weather events were significant in only a few cases, the SPMS manager may prefer to use the recent five-year average as a predictive tool for the next year. This five-year mean can be compared to the long-term mean to identify how the most recent past compares with the historical record. Caution must be used when emphasising the past five years as a mechanism for anticipating the next season s conditions. Although this period is freshest in the memory it may be misleading. A recent 5-year period that contains a distinct downward or upward trend may provide a false sense of what a season is capable of producing. When a predictive model exists, based on a tropical or central Pacific SSTA, it should be weighed more heavily in the decision process than the persistence forecast. This user-centered project (where the user defined the issues) demonstrated that if decision-makers are continually made aware of available climate data, information and forecasts, and know where to find help to enhance and interpret climatological information for their needs, more informed (and economically sound) decisions can be made. Working closely with users so they understand how to incorporate climate information into decision-making is necessary if users are to feel comfortable with altering their decisions. It appears that the number of opportunities for private-sector climatologists to link climate to weather-sensitive decisions, especially in leisure, is probably much greater than most atmospheric scientists realise. We suggest exploring these opportunities in the future. Acknowledgements This research was supported by NOAA Office of Global Programs grant #NA96GPO457. This project could not have been completed without the continual interactions between those at NIU and Mr Ross Seymour, manager of Swimming Pool Management Systems, Inc. of Woodridge, Illinois. The authors would like to thank James Angel of the MRCC for providing access to the climate data. Finally, the authors would like to acknowledge Stan Changnon and the external reviewers for their insightful comments which improved the text. 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