Evaluation of Clear-Sky Incoming Radiation Estimating Equations Typically Used in Remote Sensing Evapotranspiration Algorithms

The ground surface soil heat flux (G0) quantifies the energy transfer between the atmosphere and the ground through the land surface. However; it is difficult to obtain the spatial distribution of G0 in permafrost regions because of the limitation of in situ observation and complication of ground surface conditions. This study aims at developing an improved G0 parameterization scheme applicable to permafrost regions of the Qinghai-Tibet Plateau under clear-sky conditions. We validated several existing remote sensing-based models to estimate G0 by analyzing in situ measurement data. Based on the validation of previous models on G0; we added the solar time angle to the G0 parameterization scheme; which considered the phase difference problem. The maximum values of RMSE and MAE between “measured G0” and simulated G0 using the improved parameterization scheme and in situ data were calculated to be 6.102 W/m2 and 5.382 W/m2; respectively. When the error of the remotely sensed land surface temperature is less than 1 K and the surface albedo measured is less than 0.02; the accuracy of estimates based on remote sensing data for G0 will be less than 5%. MODIS data (surface reflectance; land surface temperature; and emissivity) were used to calculate G0 in a 10 x 10 km region around Tanggula site; which is located in the continuous permafrost region with long-term records of meteorological and permafrost parameters. The results obtained by the improved scheme and MODIS data were consistent with the observation. This study enhances our understanding of the impacts of climate change on the ground thermal regime of permafrost and the land surface processes between atmosphere and ground surface in cold regions.

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Earth Observations-Based Evapotranspiration in Northeastern Thailand

Remote Sensing ◽

10.3390/rs11020138 ◽

2019 ◽

Vol 11 (2) ◽

pp. 138 ◽

Cited By ~ 4

Author(s):

Chaolei Zheng ◽

Li Jia ◽

Guangcheng Hu ◽

Jing Lu

Keyword(s):

Remote Sensing ◽

Soil Moisture ◽

Surface Temperature ◽

Land Surface Temperature ◽

Land Surface ◽

Microwave Remote Sensing ◽

Spatiotemporal Pattern ◽

Monsoon Climate ◽

Thermal Remote Sensing ◽

Clear Sky

Thailand is characterized by typical tropical monsoon climate, and is suffering serious water related problems, including seasonal drought and flooding. These issues are highly related to the hydrological processes, e.g., precipitation and evapotranspiration (ET), which are helpful to understand and cope with these problems. It is critical to study the spatiotemporal pattern of ET in Thailand to support the local water resource management. In the current study, daily ET was estimated over Thailand by ETMonitor, a process-based model, with mainly satellite earth observation datasets as input. One major advantage of the ETMonitor algorithm is that it introduces the impact of soil moisture on ET by assimilating the surface soil moisture from microwave remote sensing, and it reduces the dependence on land surface temperature, as the thermal remote sensing is highly sensitive to cloud, which limits the ability to achieve spatial and temporal continuity of daily ET. The ETMonitor algorithm was further improved in current study to take advantage of thermal remote sensing. In the improved scheme, the evaporation fraction was first obtained by land surface temperature—vegetation index triangle method, which was used to estimate ET in the clear days. The soil moisture stress index (SMSI) was defined to express the constrain of soil moisture on ET, and clear sky SMSI was retrieved according to the estimated clear sky ET. Clear sky SMSI was then interpolated to cloudy days to obtain the SMSI for all sky conditions. Finally, time-series ET at daily resolution was achieved using the interpolated spatio-temporal continuous SMSI. Good agreements were found between the estimated daily ET and flux tower observations with root mean square error ranging between 1.08 and 1.58 mm d−1, which showed better accuracy than the ET product from MODerate resolution Imaging Spectroradiometer (MODIS), especially for the forest sites. Chi and Mun river basins, located in Northeast Thailand, were selected to analyze the spatial pattern of ET. The results indicate that the ET had large fluctuation in seasonal variation, which is predominantly impacted by the monsoon climate.

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Estimation of net shortwave radiation flux of western Himalayan snow cover during clear sky days using remote sensing and meteorological data

Remote Sensing Letters ◽

10.1080/2150704x.2013.866287 ◽

2014 ◽

Vol 5 (1) ◽

pp. 83-92 ◽

Cited By ~ 12

Author(s):

H.S. Gusain ◽

V.D. Mishra ◽

M.K. Arora

Keyword(s):

Remote Sensing ◽

Snow Cover ◽

Radiation Flux ◽

Meteorological Data ◽

Shortwave Radiation ◽

Clear Sky

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Latent heat flux estimation in clear sky days over Indian agroecosystems using noontime satellite remote sensing data

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2009.05.006 ◽

2009 ◽

Vol 149 (10) ◽

pp. 1646-1665 ◽

Cited By ~ 35

Author(s):

Kaniska Mallick ◽

Bimal K. Bhattacharya ◽

V.U.M. Rao ◽

D. Raji Reddy ◽

Saon Banerjee ◽

...

Keyword(s):

Remote Sensing ◽

Heat Flux ◽

Latent Heat ◽

Latent Heat Flux ◽

Satellite Remote Sensing ◽

Remote Sensing Data ◽

Sensing Data ◽

Clear Sky ◽

Heat Flux Estimation ◽

Flux Estimation

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Estimation of the land surface instantaneous net radiation and its diurnal cycle integrating multi-source remote sensing data under clear sky

2011 IEEE International Geoscience and Remote Sensing Symposium ◽

10.1109/igarss.2011.6049581 ◽

2011 ◽

Author(s):

Wenyu Liu ◽

Adu Gong ◽

Ji Zhou ◽

Wenfeng Zhan

Keyword(s):

Remote Sensing ◽

Diurnal Cycle ◽

Land Surface ◽

Remote Sensing Data ◽

Net Radiation ◽

Sensing Data ◽

Clear Sky

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Remote sensing of cirrus clouds and aerosols by a sun photometer in Tunisia

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-3321-2006 ◽

2006 ◽

Vol 6 (2) ◽

pp. 3321-3335

Author(s):

H. Chtioui ◽

F. B. Mansour ◽

S. Elouragini ◽

P. H. Flamant

Keyword(s):

Remote Sensing ◽

Mediterranean Coast ◽

Cirrus Clouds ◽

Main Role ◽

Clear Sky ◽

Sun Photometer ◽

The Mediterranean ◽

High Concentrations ◽

Photometric Measurements ◽

532 Nm

Abstract. Some ground based measurements of solar radiation by using a sun photometer, have been conducted in Tunisia during the period of November 2000–February 2002. Five key measurement sites were selected: Three Sites (Tunis, Sousse, Gabes) are located on the Mediterranean coast and Two sites (Gafsa, Tozeur) on the boarder of Sahara. Over a total of 149 measurement days, 21 days are identified as clear sky, 114 days as Cirrus clouds and 14 days as aerosols. Aerosols and Cirrus clouds Optical Thickness (AOT) are derived from photometric measurements at 532 nm wavelength. Spatial and temporal variabilities of AOT are presented and discussed in this paper. Cirrus clouds were frequently observed at Gafsa and Tozeur where saharan aerosol events are expected to be more frequent than cirrus clouds. The mediterranean sea and saharan aerosols are suspected to have the main role in cirrus clouds formation, by providing water vapor and high concentrations of cloud condensation and ice forming nuclei.

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Radiative Effect of Clouds at Ny-Ålesund, Svalbard, as Inferred from Ground-Based Remote Sensing Observations

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-19-0080.1 ◽

2020 ◽

Vol 59 (1) ◽

pp. 3-22 ◽

Cited By ~ 6

Author(s):

Kerstin Ebell ◽

Tatiana Nomokonova ◽

Marion Maturilli ◽

Christoph Ritter

Keyword(s):

Remote Sensing ◽

The Arctic ◽

Radiative Effect ◽

Liquid Water Path ◽

Ice Clouds ◽

Surface Warming ◽

Clear Sky ◽

Cloud Properties ◽

Cloud Radiative Effect ◽

The Difference

AbstractFor the first time, the cloud radiative effect (CRE) has been characterized for the Arctic site Ny-Ålesund, Svalbard, Norway, including more than 2 years of data (June 2016–September 2018). The cloud radiative effect, that is, the difference between the all-sky and equivalent clear-sky net radiative fluxes, has been derived based on a combination of ground-based remote sensing observations of cloud properties and the application of broadband radiative transfer simulations. The simulated fluxes have been evaluated in terms of a radiative closure study. Good agreement with observed surface net shortwave (SW) and longwave (LW) fluxes has been found, with small biases for clear-sky (SW: 3.8 W m−2; LW: −4.9 W m−2) and all-sky (SW: −5.4 W m−2; LW: −0.2 W m−2) situations. For monthly averages, uncertainties in the CRE are estimated to be small (~2 W m−2). At Ny-Ålesund, the monthly net surface CRE is positive from September to April/May and negative in summer. The annual surface warming effect by clouds is 11.1 W m−2. The longwave surface CRE of liquid-containing cloud is mainly driven by liquid water path (LWP) with an asymptote value of 75 W m−2 for large LWP values. The shortwave surface CRE can largely be explained by LWP, solar zenith angle, and surface albedo. Liquid-containing clouds (LWP > 5 g m−2) clearly contribute most to the shortwave surface CRE (70%–98%) and, from late spring to autumn, also to the longwave surface CRE (up to 95%). Only in winter are ice clouds (IWP > 0 g m−2; LWP < 5 g m−2) equally important or even dominating the signal in the longwave surface CRE.

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