Abstract
Accurate estimate of the surface longwave radiation is important for the surface radiation budget, which in turn controls evaporation and sensible heat fluxes. Regional land use changes can impact local weather conditions; for example, heterogeneous land use patterns and temporal changes in atmospheric circulation patterns would affect air temperature and water vapor pressure, which are more commonly used as inputs in existing models for estimating downward longwave radiation (LWd). In this study, first, we analyzed the cloud cover and land use covers impacts onLWd. Next,LWdon all-sky conditions were developed by using the existing land use-adapted model and cloud cover data from the region of Saint Johns River Water Management District (SJRWMD), FL. The results show that factors, such as, seasonal effects, cloud cover, and land use, are of importance in the estimation ofLWdand they cannot be ignored when developing a model forLWdprediction. The all-sky land use-adapted model with all factors taken into account performs better than other existing models statistically. The results of the statistical analyses indicated that the BIAS, RMSE, MAE, and PMRE are −0.18 Wm−2, 10.81 Wm−2, 8.00 Wm−2, and 2.30%; −2.61 Wm−2, 14.45 Wm−2, 10.64 Wm−2, and 3.19%; −0.07 Wm−2, 10.53 Wm−2, 8.03 Wm−2, and 2.27%; and −0.62 Wm−2, 13.97 Wm−2, 9.76 Wm−2, and 2.87% for urban, rangeland, agricultural, and wetland areas, respectively.
Highlights
Accurate estimate of downward longwave radiation (LWd) is necessary for calculating the net radiation, which in turn modulates the magnitude of the surface energy budgets, including latent heat [1]
Due to poor vertical resolution of water vapor data and difficulties associated with the atmospheric emissivity and temperature, many reasonably successful techniques have been developed in recent decades that estimate LWd based on the screen-level humidity and air temperature measurements
The wet season in Florida starts from end of May to middle of October while the rest is classified as dry season
Summary
Accurate estimate of downward longwave radiation (LWd) is necessary for calculating the net radiation, which in turn modulates the magnitude of the surface energy budgets, including latent heat [1]. This knowledge is required for (a) forecasting of temperature variation, frost occurrence, and cloudiness, (b) estimation of climate variability and global warming, and (c) design of radiant cooling systems [1, 2]. Several parameterizations have been developed for LWd using synoptic observations [6,7,8,9,10,11,12,13,14,15]
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