Components of near-surface energy balance derived from satellite soundings – Part 1: Noontime net available energy

Abstract

This paper introduces a relatively simple method for recovering global fields of monthly midday (13:30 LT) near-surface net available energy (the sum of the sensible and latent heat flux or the difference between the net radiation and surface heat accumulation) using satellite visible and infrared products derived from the AIRS (Atmo-spheric Infrared Sounder) and MODIS (MODerate Resolution Imaging Spectroradiometer) platforms. The method fo-cuses on first specifying net surface radiation by considering its various shortwave and longwave components. This was then used in a surface energy balance equation in conjunction with satellite day-night surface temperature difference to derive 12 h discrete time estimates of surface system heat capacity and heat accumulation, leading directly to retrieval for surface net available energy. Both net radiation and net available energy estimates were evaluated against ground truth data taken from 30 terrestrial tower sites affiliated with the FLUXNET network covering 7 different biome classes. This revealed a relatively good agreement between the satellite and tower data, with a pooled root-mean-square deviation of 98 and 72 W m −2 for monthly 13:30 LT net radiation and net available energy, respectively, although both quantities were underestimated by approximately 25 and 10 %, respectively , relative to the tower observation. Analysis of the individual shortwave and longwave components of the net radiation revealed the downwelling shortwave radiation to be main source of this systematic underestimation.

Net Surface Shortwave Radiation Retrieval Using Random Forest Method With MODIS/AQUA Data

“…It is widely recognized that remote sensing technology has become a highly effective and convenient method for retrieving land surface radiation [4][5][6]. In recent years, numerous methods for accurate estimation of NSSR, including a statistical/empirical method [7] and a physically based method [8][9][10], have been explored and developed.…”

Upscaling instantaneous to daily evapotranspiration using modelled daily shortwave radiation for remote sensing applications: an artificial neural network approach

“…However, we evaluate the performance in consideration with overpass time of polar orbiting satellites commonly used in operational ET mapping, namely MODIS and LANDSAT. By choosing to use data distributed over different ecosystems and climate zones, we are faced with two problems: (1) changing cloud conditions across ecosystems and (2) varying energy balance closure (EBC) requirements for the fluxes in different ecosystems (Foken et al, 2006;Franssen et al, 2010;Mauder and Foken, 2006;Wilson et al, 2002). Currently, information on cloudiness is obtainable from geostationary meteorological satellites, at hourly to 3 h time steps, e.g.…”

Reintroducing radiometric surface temperature into the Penman‐Monteith formulation

“…per 6 1 K uncertainty in T R ) [Mallick et al, 2015], and, therefore additional uncertainties expected from T R induced through / (5 R N 2 G) would be of minor importance.…”

“…Overall, the high sensitivity of the fluxes and conductances to T R stresses the need for high‐quality T R data in surface energy balance modeling. It is also important to mention that uncertainties in T R will also amplify the uncertainties both in R N and G , but to a small extent (to the order of 2–6% per ± 1 K uncertainty in T R ) [ Mallick et al ., ], and, therefore additional uncertainties expected from T R induced through ϕ (= R N − G ) would be of minor importance.…”