Publications

Munkhjargal, M; Menzel, L (2019). Estimating daily average net radiation in Northern Mongolia. GEOGRAFISKA ANNALER SERIES A-PHYSICAL GEOGRAPHY, 101(2), 177-194.

Abstract
Net radiation is a key component of surface radiation balance and has a strong influence on hydrological processes via evapotranspiration. In this study, daily average net radiation (Rn-mean) for all-sky conditions was investigated as a function of the estimated daily average global radiation (GR(mean)) during the summers of 2011 and 2012 (128 days total) in the Sugnugur Valley of Northern Mongolia. We present a simple alternative remote sensing approach that considers factors such as topography, cloud fraction, cloud optical thickness and surface albedo. First, a geometric model for the simulation of daily average global radiation (GR(CS:mean)) for clear-sky conditions was applied on a daily basis. It considers topographical effects, such as slope, azimuth and elevation. GR(mean) was then derived for all-sky conditions by coupling the averaged atmospheric products of MODIS. Finally, Rn-mean was obtained as a function of the simulated GR(mean) using the linear regression parameters found at a permanent observation site. The results were validated with the data from a nearby temporary observation site. The root mean square errors (RMSE) were 44 and 52 Wm(-2) for GR(mean) and 18 and 25 Wm(-2) for Rn-mean at the two different sites. This methodology requires few observations and offers a simple means for estimating GR(mean) with high spatial (30 m) and temporal (daily) resolution under any sky conditions in the absence of ground measurements. Furthermore, Rn-mean can be modeled from the simulated GR(mean) at regional or watershed scales where ground observations exist at one site at least.

DOI:
10.1080/04353676.2019.1583498

ISSN:
0435-3676