Impact of Synoptic Weather Systems on the Surface Energy Budget over a Large Inland Water Body

¹Justin Bonds, ²Raleigh Grysko, ²Zhongming Gao, ²Heping Liu

¹Jackson State University, Department of Physics, Atmospheric Sciences & Geoscience, Jackson, MS

²Washington State University, Laboratory for Atmospheric Research, Pullman, WA

This work was supported by the National Science Foundation’s REU program under

grant number AGS-1461292.

A large inland water body’s surface energy budget is subjectto a variety of changing meteorological conditions, which areusually associated with frequent passages of synopticweather systems. The water surface energy budget consistsof net radiation, latent heat flux, sensible heat flux, and heatstorage in water. Therefore, it is important to understandhow the surface energy budget is impacted by varyingmeteorological conditions. We analyzed diurnal and monthlychanges in the water surface energy budget with the datacollected from an eddy covariance system over the RossBarnett Reservoir in Ridgeland, Mississippi. We studied theinfluence of the passages of synoptic weather systems on thewater’s surface energy budget during the period of Marchand April of 2008.

● Understand water surface energy budget and analyze diurnal cycles in the surface energy budget.

● Determine what factors contribute to significant fluctuations in the surface energy budget.

● Determine how the passage of cold fronts affect the surface energy budget

● Examine how the surface energy budget will vary with different synoptic weather systems.

Figure 4a: Four day diurnal analysis of surface energy budget for March 18th-21st. Figure 4b: Air Temperature vs Water skin Temperature for March 18th-21st. Figure 4c: Pressure vs Wind Speed for March 18th-21st.

Figure 5a: Four day diurnal analysis of surface energy budget for April17th-19th. Figure 5b: Air Temperature vs Water skin Temperature for April17th-19th. 5c: Pressure vs Wind Speed for April 17th-19th.

Data that the Ross Barnett Reservoir flux tower collected in2008 were analyzed from March 1st to March 31st and April 1st

to April 30th. A CNR4 net radiometer measured net radiation.An eddy covariance system measured sensible heat and latentheat fluxes. Other meteorological variables were alsomeasured, including wind speed, air temperature, humidity,pressure, and water surface temperature. Twelve cold frontswere observed during the two month period; two of whichwere analyzed in greater detail. Synoptic weather maps wereused to determine synoptic weather conditions for any givenday during this period.

● Out of 12 cold fronts found to have passed the RBR area during the months of March and April, 2008, the two used in thisanalysis were chosen because of their key differences in size and strength.

● The cold front observed in March was significantly larger, lower in pressure, and took longer to traverse through the state.● Weak cold fronts had less of an impact on surface energy budget than stronger cold fronts.● Sensible and latent heat fluxes were typically above average after the passage of cold fronts.● Instances where sensible heat fluxes were enhanced when the air temperature fell significantly lower than the water skin

temperature, causing heat release from the relatively warm water.Figure 1b: The Ross BarnettReservoir eddy covariance fluxtower

Figure 2a: Synoptic Weather Map of a largelow pressure system moving throughcontinental U.S. on March 18th, 2008.

Figure 2b: Doppler Radar Image of cold frontpassage through southeastern United States andMississippi on March 19th, 2008.

Figure 3a: Synoptic Weather map of a lowpressure system moving through continentalU.S. on April 18th, 2008.

Introduction

Objectives

Figure 3b: Doppler Radar image of cold frontpassage through southeastern United States andMississippi on April 18th, 2008.

Acknowledgements

Methods

Data

Figure 1a: Aerial view of RossBarnett Reservoir and the FluxTower Site as denoted astriangle. The flux tower islocated at least 2 km from shore

Conclusion

a) a)

b) b)

c)

● Cold fronts affect the surface energy budget by decreasing net radiation and increasing sensible and latent heat. The strength of these effects can be determined by the size of the system, differences in pressure, and its speed.

● Latent heat fluxes were enhanced by the passage of cooler, dryer air over the relatively warm and humid water.