A Physical-Based Algorithm for Retrieving Land Surface Temperature From Moon-Based Earth Observation
16 Apr 2020-IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 13, pp 1856-1866
TL;DR: A modified physical-based method of LST retrieval from passive microwave data was developed for wide viewing zenith angles, and the LST and emissivity can be simultaneously estimated through the analysis of various atmospheric and ionosphere parameters.
Abstract: Land surface temperature (LST) is a key parameter and plays an important role in hydrology, ecology, environment, and biogeochemistry. It is difficult for the existing satellites to acquire global LST with spatial and temporal consistency. The Moon-based Earth observation platform with a long life, large coverage can observe continuously the Earth, and obtain the global-scale LST. At present, various approaches for retrieving LST from passive microwave remote sensing data have been developed for the satellite remote sensing data with small and constant viewing zenith angle, however, the Moon-based Earth observation platform located outside the Earth's ionosphere has the viewing zenith angle of 0–90°. In this study, a modified physical-based method of LST retrieval from passive microwave data was developed for wide viewing zenith angles, and the LST and emissivity can be simultaneously estimated through the analysis of various atmospheric and ionosphere parameters. Three types of data, including the FengYun-3B satellite microwave radiation imager data, the multichannel Advanced Microwave Scanning Radiometer data, and Moon-based microwave radiation simulation data with the viewing zenith angles of 52–53°, 55°, and 0–90°, respectively, were used to retrieve LST. Results show that the estimation accuracy of LST decreases with the increase of viewing zenith angle. The 23.8 and 36.5 GHz brightness temperature is optimum for the LST estimation under a large-scale viewing zenith angle, and the root mean square errors of the LST are 5.18, 5.44, and 4.79 K, respectively.
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01 Dec 2013
TL;DR: In this paper, the uncertainties of current estimates of global Ld at monthly to decadal timescales and its global climatology and trends during the past decades by a synthesis of the existing observations, reanalyses, and satellite products were quantified.
Abstract: [1] Atmospheric downward longwave radiation at the surface (Ld) varies with increasing CO2 and other greenhouse gases. This study quantifies the uncertainties of current estimates of global Ld at monthly to decadal timescales and its global climatology and trends during the past decades by a synthesis of the existing observations, reanalyses, and satellite products. We find that current Ld observations have a standard deviation error of ~3.5 W m−2 on a monthly scale. Observations of Ld by different pyrgeometers may differ substantially for lack of a standard reference. The calibration of a pyrgeometer significantly affects its quantification of annual variability. Compared with observations collected at 169 global land sites from 1992 to 2010, the Ld derived from state-of-the-art satellite cloud observations and reanalysis temperature and humidity profiles at a grid scale of ~1° has a bias of ±9 W m−2 and a standard deviation of 7 W m−2, with a nearly zero overall bias. The standard deviations are reduced to 4 W m−2 over tropical oceans when compared to Ld observations collected by 24 buoy sites from 2002 to 2011. The −4 W m−2 bias of satellite Ld retrievals over tropical oceans is likely because of the overestimation of Ld observations resulting from solar heating of the pyrgeometer. Our best estimate of global means Ld from 2003 to 2010 are 342 ± 3 W m−2 (global), 307 ± 3 W m−2 (land), and 356 ± 3 W m−2 (ocean). Estimates of Ld trends are seriously compromised by the changes in satellite sensors giving changes of water vapor profiles.
7 citations
TL;DR: To explore whether a microwave radiometer is suitable for the MEO platform, the land surface temperature (LST) distribution at different times is estimated and the design parameters of the Moon-based microwave radiometers (MBMR) are analyzed based on the LST retrieval.
Abstract: Increasing attention is being paid to the monitoring of global change, and remote sensing is an important means for acquiring global observation data. Due to the limitations of the orbital altitude, technological level, observation platform stability and design life of artificial satellites, spaceborne Earth observation platforms cannot quickly obtain global data. The Moon-based Earth observation (MEO) platform has unique advantages, including a wide observation range, short revisit period, large viewing angle and spatial resolution; thus, it provides a new observation method for quickly obtaining global Earth observation data. At present, the MEO platform has not yet entered the actual development stage, and the relevant parameters of the microwave sensors have not been determined. In this work, to explore whether a microwave radiometer is suitable for the MEO platform, the land surface temperature (LST) distribution at different times is estimated and the design parameters of the Moon-based microwave radiometer (MBMR) are analyzed based on the LST retrieval. Results show that the antenna aperture size of a Moon-based microwave radiometer is suitable for 120 m, and the bands include 18.7, 23.8, 36.5 and 89.0 GHz, each with horizontal and vertical polarization. Moreover, the optimal value of other parameters, such as the half-power beam width, spatial resolution, integration time of the radiometer system, temperature sensitivity, scan angle and antenna pattern simulations are also determined.
3 citations
Journal Article•
TL;DR: In this paper, the authors derived the critical frequency of ionosphere in linearity condition and the atmospheric refractive index formula for high power microwave (HPM) propagation through ionosphere.
Abstract: The characteristic of high power microwave(HPM) propagation through ionosphere is mainly determined by the diversification of the atmospheric refractive index,while the refractive index has positive correlation with the electron concentration at corresponding propagation layer.The critical frequency of ionosphere in linearity condition and the atmospheric refractive index formula are derived.The electron concentration and the atmospheric refractive index are numerically simulated based on ionospheric electron concentration distributing model.The diversification of the refractive index and the refractive index gradient relating to the altitude are also analyzed, and experiment has been taken under low power microwave condition which validates that the corrected value is closer to the practicality than the value operated from general theory.Hence the altitude,elevation and incept power of HPM propagation can be modified by the theory of this paper,which can also provide theoretic reference to practical HPM propagation.
2 citations
1 citations
TL;DR: In this paper , the effect of the sampling interval on irradiance was analyzed based on a radiation transfer model, and the results showed that the measurements of the MWFOV radiometer can reveal the variation of irradiance on hourly, daily and monthly time scales.
Abstract: Moon-based Earth radiation observation can provide longer-term, continuous multi-angle measurements for the Earth’s outward radiative flux. In addition, the large distance between the Moon and Earth means that the radiation can be monitored by a non-scanning Moon-based Wide Field-of-View (MWFOV) radiometer considering the Earth as one pixel. In order to parameterize the radiometer, studying the effect of the temporal sampling interval on irradiance is of great importance. In this work, based on radiation transfer model, simulated irradiance time series from March 2000 to December 2020 were analyzed. Then, we used them to reveal the effects of the sampling interval on irradiance. The results show that the measurements of the MWFOV radiometer can reveal the variation of irradiance on hourly, daily and monthly time scales, and the high-frequency measurements can reflect the variation of scene types in the MWFOV-viewed area. In order to obtain more meaningful measurements, the radiation resolution of the MWFOV radiometer should be better than 0.5 mW∙m−2 with an accuracy of 1% or better in the future actual design, and the sampling interval should be less than 1 h, which can ensure that 97% of the surface area can be sampled more than nine times per day for longwave radiation. The derived results in this study could facilitate Moon-based data processing and the determination of the sampling interval and radiation resolution of an MWFOV under a certain manufacturing cost and error limit.
References
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TL;DR: In this paper, an alternative to thermal infrared satellite sensors for measuring land surface temperature (Ts) is presented, where the 37 GHz vertical polarized brightness temperature is used to derive Ts because it is considered the most appropriate microwave frequency for temperature retrieval.
Abstract: [1] An alternative to thermal infrared satellite sensors for measuring land surface temperature (Ts) is presented. The 37 GHz vertical polarized brightness temperature is used to derive Ts because it is considered the most appropriate microwave frequency for temperature retrieval. This channel balances a reduced sensitivity to soil surface characteristics with a relatively high atmospheric transmissivity. It is shown that with a simple linear relationship, accurate values for Ts can be obtained from this frequency, with a theoretical bias of within 1 K for 70% of vegetated land areas of the globe. Barren, sparsely vegetated, and open shrublands cannot be accurately described with this single channel approach because variable surface conditions become important. The precision of the retrieved land surface temperature is expected to be better than 2.5 K for forests and 3.5 K for low vegetation. This method can be used to complement existing infrared derived temperature products, especially during clouded conditions. With several microwave radiometers currently in orbit, this method can be used to observe the diurnal temperature cycles with surprising accuracy.
284 citations
TL;DR: In this article, the reflection, absorption, and transmission of microwaves by a magnetized, steady-state, two-dimensional, non-uniform plasma slab is studied and a discussion on the effect of various plasma parameters on the reflected power, absorbed power, and transmitted power is presented.
Abstract: The reflection, absorption, and transmission of microwaves by a magnetized, steady-state, two-dimensional, nonuniform plasma slab is studied. A discussion on the effect of various plasma parameters on the reflected power, absorbed power, and transmitted power is presented. The nonuniform plasma slab is modeled by a series of subslabs. Even though it is assumed that the number density is constant in each subslab, the overall number density profile across the whole slab follows a parabolic function. The partial reflection coefficient at each subslab boundary is computed along with the absorption at each subslab. The total reflected, absorbed, and transmitted powers are then deduced and their functional dependence on the number density, collision frequency, and angle of propagation is studied. >
245 citations
"A Physical-Based Algorithm for Retr..." refers background in this paper
...These electrons and ions will also cause the attenuation of incident microwave radiation energy due to their collisions in the ionosphere [43]–[48]....
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TL;DR: In this paper, a regression analysis comparing all of the SSM/I channels and minimum screen air temperatures (representing the surface temperature) showed good correlations, with root-mean-square errors of 2-3 degC.
Abstract: Passive microwave brightness temperatures from the Defense Meteorological Space Program Special Sensor Microwave/Imager (SSM/I) were used to determine surface temperature over land areas in the central plains of the United States. A regression analysis comparing all of the SSM/I channels and minimum screen air temperatures (representing the surface temperature) showed good correlations, with root-mean-square errors of 2-3 degC. Pixels containing large amounts of water, snow, and falling rain, as classified with SSM/I brightness temperatures, were excluded from the analysis. The use of independent ground truth data such as soil moisture or land surface type was not required to obtain the correlations between brightness temperatures and surface temperatures. >
178 citations
"A Physical-Based Algorithm for Retr..." refers background in this paper
...of 37 GHz acquired by satellite was optimal for retrieving LST [6]–[8], and the results of this study showed that two frequencies of 23....
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...transmission theory and microwave propagation in the ionosphere [6]–[14], [17]–[19], the total radiant energy received by a...
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...presented that the scattering and absorption of water vapor, cloud particles and rain have little effect on the low-frequency microwave in the atmosphere [6]....
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TL;DR: In this article, a method has been developed to calculate near-surface temperature using measurements from the Special Sensor Microwave/Imager (SSM/I) using training datasets.
Abstract: The worldwide network of in situ land surface temperatures archived in near-real time at the National Climatic Data Center (NCDC) has limited applications, since many areas are poorly represented or provide no observations. Satellite measurements offer a possible way to fill in the data voids and obtain a complete map of surface temperature over the entire globe. A method has been developed to calculate near-surface temperature using measurements from the Special Sensor Microwave/Imager (SSM/I). To accomplish this, the authors identify numerous surface types and make dynamic adjustments for variations in emissivity. Training datasets were used to define the relationship between the seven SSM/I channels and the near-surface temperature. For instance, liquid water on the surface reduces emissivity; therefore, the authors developed an adjustment to correct for this reduction. Other surface types (e.g., snow, ice, and deserts) as well as precipitation are identified, and numerous adjustments and/or f...
176 citations
"A Physical-Based Algorithm for Retr..." refers methods in this paper
...developed a LST retrieval algorithm using SSM/I data [12], which adjusted the temperature for variations in surface emissivity....
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TL;DR: In this article, a strong linear relationship is found between Special Sensor Microwave/Imager (SSM/I) microwave (19 and 37 GHz) surface emissivities at horizontal and vertical polarizations over snow-and ice-free land surfaces.
146 citations