Abstract
Surface shortwave (SW) irradiation is the primary driving force of energy exchange in the atmosphere and land interface. The global climate is profoundly influenced by irradiation changes due to the special climatic condition in Antarctica. Remote-sensing retrieval can offer only the instantaneous values in an area, whilst daily cycle and average values are necessary for further studies and applications, including climate change, ecology, and land surface process. When considering the large values of and small diurnal changes of solar zenith angle and cloud coverage, we develop two methods for the temporal extension of remotely sensed downward SW irradiance over Antarctica. The first one is an improved sinusoidal method, and the second one is an interpolation method based on cloud fraction change. The instantaneous irradiance data and cloud products are used in both methods to extend the diurnal cycle, and obtain the daily average value. Data from South Pole and Georg von Neumayer stations are used to validate the estimated value. The coefficient of determination (R2) between the estimated daily averages and the measured values based on the first method is 0.93, and the root mean square error (RMSE) is 32.21 W/m2 (8.52%). As for the traditional sinusoidal method, the R2 and RMSE are 0.68 and 70.32 W/m2 (18.59%), respectively The R2 and RMSE of the second method are 0.96 and 25.27 W/m2 (6.98%), respectively. These values are better than those of the traditional linear interpolation (0.79 and 57.40 W/m2 (15.87%)).
Highlights
Solar shortwave (SW) radiation reaching the surface of the Earth is the primary energy source, which plays a significant role in surface energy balance, temperature variations, hydrological cycle, and terrestrial net primary productivity [1,2,3]
We can calculate the diurnal variation in solar zenith angle (SZA) at different dates and latitudes
SW surface radiation budget data sets are derived on a 1◦ × 1◦ global grid with two sets of algorithms, known as primary SW algorithm and Langley parameterized SW algorithms (LPSA) [38,39]
Summary
Solar shortwave (SW) radiation reaching the surface of the Earth is the primary energy source, which plays a significant role in surface energy balance, temperature variations, hydrological cycle, and terrestrial net primary productivity [1,2,3]. Irradiation flux data are required in many regional climate system models and applications as input parameters [12,13,14]. Satellite remote sensing technique is a suitable way to obtain solar irradiance data at continent scale [16]. Ecology, and land surface process models require daily average or diurnal cycle data. Numbers of methods, including empirical method [17], sinusoidal method [18,19,20], meteorological parameter interpolation method [21,22], lookup table (LUT) method [23], quadratic polynomial regression method [24], and polar orbit and static satellite data fusion method, have been developed to obtain daily values [25]
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