1. Rooftop Weather Stations As Viable Mesonet Contributors - Validation Experiments Paul Ruscher and Ashlee Hicks 1 Department of Meteorology, The Florida State University INTRODUCTION The need for a surface based, dense meteorological observation network in Florida has long been recognized. In 2002, scientists across the state of Florida joined together with the National Science Foundation, the REALM Project, the Florida State University, and other agencies to create the Miami-Dade Mesonet. This research is a study of the instruments used in the Miami- Dade Mesonet (the Davis Vantage Pro Weather Instruments) and of the data collected by the mesonet. The goal is to prove that though the Davis Weather Instruments are inexpensive, and the placement of the instruments in the mesonet do not meet all the operational standards and procedures for surface observing, that the mesonet can still produce accurate and practical observations. This research will present an overall assessment of the accuracy and quality of the data collected. First, an internal examination of three Davis weather instruments was conducted on the roof of the James J. Love Math-Meteorology building on the FSU campus, in order to evaluate the integrity of the equipment in a controlled setting with varying parameters. Next, quality assurance procedures were run on the actual data from the Miami-Dade Mesonet to determine how well the mesonet compares with Automatic Surface Observing Systems (ASOS). Then, four case studies were conducted to examine the ability of the instruments to detect specific types of weather events, including a tornado outbreak, a record high temperature in mid- winter, a heavy rainfall event, and a sea breeze passage case. Each study evaluated a different aspect of the mesonet stations, leading to positive results proving that the systems provide operationally significant observations. The REALM Project was extended in the summer of 2005 through the Florida Panhandle and parts of central Florida, which will greatly increase observational coverage in data sparse regions in rural areas, especially in northwest Florida. Figure 2. A time series of the maximum (top packet of lines) and minimum (bottom packet of lines) temperatures for all FSU Roof Experiment stations during Phase I. Temperature, in degrees Celsius, is on the y- axis, and dates are labeled on the x-axis. The total mean is the average of the Tower, Complete, Non- aspirated, and Unshielded stations. Precipitation, in inches, recorded from the Complete station is also plotted on the x-axis. P2.13 Figure 1. Davis Vantage Pro2 wireless fan-aspirated automated weather station, courtesy of Davis Instruments (retrieved from their online catalog at http://www.davisnet.com/weather/produc ts/weather_product.asp?pnum=06153). ACKNOWLEDGEMENTS Gratitude is due to Russell Chadwick, Patty Miller, and Michael Barth from MADIS, as well as Steve Dimse for all of their data access and support. Recognition is owed to Francisco Vargas for his time in the initiation of the Miami-Dade Mesonet and the upkeep of the stations. Finally, a special thanks is due to the Leon County 4-H Program for their generous grant from the Florida 4-H Foundation Disaster Awareness Prepared Program, which allowed for the commencement of the REALM2 Project, as well as the equipment assistance from Mr. Bob Broedel. Thanks also to Rusty Pfost and Pablo Santos of the NWS MFL WFO for their participation in the project and for useful perspectives. Finally, our thanks to all the participating teachers and other school employees for their assistance. Some of this research was supported by a grant from the Florida Division of Emergency Management, and the NSF also provided partial support from EHR grant 0119899. THE SITES & THE RESULTS Figure 3. (LEFT) Miami-Dade area topography in meters, including Mesonet and COOP stations, as well as ASOS sites. The Miami-Dade urban area is generally located within the black outlines. Figure 6. The daily minimum temperature differences, in degrees Celsius, between the Unshielded Station, the remaining roof stations, and the TLH ASOS are plotted above for Phase I of the Roof Experiment. The average minimum temperature differences listed in the box on the top of the chart are color coordinated according to each station comparison. A record temperature event occurred in Feburary 2003, with the arrival of the earliest day on record of 90°F temperatures. Our network stations captured this event particularly well, with no warm bias (what might have been suspected for rooftop stations). In this study, we concentrate on the quality of maximum and minimum temperature data from rooftop automated weather stations by comparing to COOP, ASOS, and other MADIS sites across Miami-Dade Florida. We also examine the relationship between daytime temperature and solar insolation, wind speed, and relative humidity (all also available from the same automated station. We also examine the separate and combined role of fan aspiration for temperature and protection using radiation shield. An examination of systematic and random errors was conducted at FSU in Tallahassee in order to help us understand how systematically good (or bad) our Miami area temperatures were during the operation of the REALM network. Figure 5. The daily maximum temperature differences, in degrees Celsius, between the Unshielded Station, the remaining roof stations, and the TLH ASOS are plotted above for Phase I of the Roof Experiment. The average maximum temperature differences listed in the box on the top of the chart are color coordinated according to each station comparison. Figure 4. (RIGHT) Miami-Dade Mesonet, ASOS, and COOP sites maximum recorded temperatures on 28 February 2003. Figure 8. A scatter plot of the Complete Station ’ s diurnal temperature range (in °C), calculated from the maximum minus the minimum temperature, versus the daily mean relative humidity. The equation of the trendline is shown in the upper right corner. Figure 9. This graph compares The Complete station versus The Non- aspirated station maximum temperature for Phase I of the roof experiment. A trend line was overlaid, and the equation of the least-squares best fit line is shown above. Figure 10. As in Figure 9, but for the Complete station versus The Unshielded station. Figure 11. The temperature difference (in °C) between the Complete and the Tower stations compared to the afternoon average wind speeds (in m/s). The equation of the line is shown in the top left corner. Figure 7. A chart of the daily maximum and minimum temperatures for the Tower, Non-Aspirated II, and the Complete II stations, as well as the TLH ASOS during Phase III of the FSU Roof Experiment. Figure 13. A scatter plot of the Complete Station ’ s diurnal temperature range (in °C), calculated from the maximum minus the minimum temperature, versus the daily mean relative humidity. The equation of the trendline is shown in the upper right corner. Figure 12. This figure shows the percentage of QC flags that were given to “ bad ” data from the Miami-Dade Mesonet from 2003 through 2004, according to MADIS.