Advances in Monitorinq Methods of Downward Surface Net Radiation

Downward surface net radiation,the net energy of the earth's surface obtained through shortwave and longwave radiation process,is the main driving force for material and energy cycle in the whole earth system.In this study,the main research results of monitoring methods of downward surface net radiation at home and abroad in recent decades have been summarized,and main remote sensing radiation products produced according to various sensors have been introduced.Moreover,the monitoring methods of downward shortwave and long-wave radiation have been discussed,and their principles,advantages and disadvantages have been analyzed to provide scientific references for further study of downward surface solar net radiation in future.

Difference in the Interdecadal Variability of Spring and Summer Sensible Heat Fluxes over Northwest China

The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the spring sensible heat flux over Northwest China was greater during the period from the late 1970s to the 1990s than during the period from the 1960s to the mid-1970s. The summer sensible heat flux was smaller in the late 1980s through the 1990s than it was in the 1970s through the early 1980s. Both the spring and summer land-air temperature differences over Northwest China displayed an obvious interdecadal increase in the late 1970s. Both the spring and summer surface wind speeds experienced an obvious interdecadal weakening in the late 1970s. The change in the surface wind speed played a more important role in the interdecadal variations in sensible heat flux during the summer, whereas the change in the land-air temperature difference was more important for the interdecadal variations in sensible heat flux in the spring. This difference was related to seasonal changes in the mean land-air temperature difference and the surface wind speed. Further analysis indicated that the increase in the spring land surface temperature in Northwest China was related to an increase in surface net radiation.

Estimating high-spatial resolution surface daily longwave radiation from the instantaneous Global LAnd Surface Satellite(GLASS)longwave radiation product

In this paper,time extension methods,originally designed for clear-sky land surface conditions,are used to estimate high-spatial resolution surface daily longwave(LW)radiation from the instantaneous Global LAnd Surface Satellite(GLASS)longwave radiation product.The performance of four time methods were first tested by using ground based flux measurements that were collected from 141 global sites.Combined with the accuracy of daily LW radiation estimated from the instantaneous GLASS LW radiation,the linear sine interpolation method performs better than the other methods and was employed to estimate the daily LW radiation as follows:The bias/Root Mean Square Error(RMSE)of the linear sine interpolation method were−6.30/15.10 W/m^(2)for the daily longwave upward radiation(LWUP),−1.65/27.63 W/m2 for the daily longwave downward radiation(LWDN),and 4.69/26.42 W/m^(2)for the daily net longwave radiation(LWNR).We found that the lengths of the diurnal cycle of LW radiation are longer than the durations between sunrise and sunset and we proposed increasing the day length by 1.5 h.The accuracies of daily LW radiation were improved after adjusting the day length.The bias/RMSE were−4.15/13.74 W/m2 for the daily LWUP,−1.3/27.52 W/m^(2)for the daily LWDN,and 2.85/25.91 W/m^(2)for the daily LWNR.We are producing long-term surface daily LW radiation values from the GLASS LW radiation product.