Surface Heat Flux Variations Research Articles

The variation of surface heat fluxes during Arabian Sea monsoon experiment

Direct measurement of radiative fluxes on board ORV Sagar Kanya were made during Arabian Sea Monsoon Experiment (ARMEX) phases I & II for a total of 120 days. The variation of surface heat fluxes has been studied in this article. Negative values of net heat flux are predominant during the active phase of monsoon. The incoming short wave radiation is minimum on 3 August 2002 and on 8 June 2003 in association with heavy rainfall. The SST is 2° C higher during Warm Pool Experiment (WPE) (ARMEX-II 2003) than Offshore Trough Experiment (OSTE)-ARMEX-2002. Also, the mean SST is 2.4° C higher during WPE than OSTE in June. During OSTE, SST is showing negative correlation (- 0.75) with wind speed and positive correlation (0.52 and 0.48) with latent heat and net heat fluxes respectively. Where as during WPE, the SST is having a positive correlation (0.74) with wind speed and a negative correlation with latent heat flux (- 0.42) and net heat flux (- 0.48). During WPE, advection is strong than the vertical net heat flux. The mean net heat flux is positive during March, April and May and is negative during June, July and August during the OSTE as well as WPE.

Diurnal and inter-monthly variation of land surface heat fluxes over the central Tibetan Plateau area

The energy and water cycle over the Tibetan Plateau play an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. Using field observational data observed from the GAME/Tibet (GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Tibetan Plateau) and the CAMP/Tibet (CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan Plateau), some results on the local surface energy partitioning (diurnal variation, inter-monthly variation and vertical variation etc.) are presented in this study. The study on the regional surface energy partitioning is of paramount importance over heterogeneous landscape of the Tibetan Plateau and it is also one of the main scientific objectives of the GAME/Tibet and the CAMP/Tibet. Therefore, the regional distributions and their inter-monthly variations of surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) are also derived by combining NOAA-14/AVHRR data with field observations. The derived results were validated by using the ground truth, and it shows that the derived regional distributions and their inter-monthly variations of land surface heat fluxes are reasonable by using the method proposed in this study. Further improvement of the method and its applying field were also discussed.

Variability of surface heat flux over the Indian Ocean

The variability of surface heat flux over the Indian Ocean is investigated using in situ observational data. First, the Indian Ocean is divided into eight regions and the power spectra of surface heat fluxes are calculated for each region. Consequently it is shown that the surface heat flux over the Indian Ocean has three characteristic timescales: (1) the high frequency timescale (periods shorter than 20 months), (2) the middle frequency timescale (periods between 20 and 60 months), and (3) the low frequency timescale (periods longer than 60 months). Seasonal variation is dominant for the high frequency timescale, with shortwave radiation and the latent heat flux being the principal components of the variability at this timescale. Furthermore, the seasonal variation can be divided into three patterns depending on the region. The variation of shortwave radiation and the latent heat flux are also dominant in the middle‐frequency timescale. In some regions, heat flux variation for this timescale appears to be associated with El Niño. For the low‐frequency timescale, the latent heat flux is dominant. It should be noted that the heat flux from the ocean to the atmosphere has clearly increased since the late 1970s as a result of increases in wind speeds and the specific humidity difference.

Improved fast-response heat transfer instrumentation for short-duration wind tunnels

This paper describes the recent innovations associated with the fabrication and application of fast-response heat flux gauges in short-duration wind-tunnel facilities in Oxford. This work has been driven by the need to measure the heat transfer in an environment with large spatial and temporal variations in surface heat flux, caused by a flow-field that has significant high-frequency periodic fluctuations in both recovery temperature and heat transfer coefficient (namely, an axial flow turbine). A new approach to the fabrication of miniature surface heat flux thin-film gauges is described; this involves the use of a pulse laser to ablate (etch) the gauge and connecting track patterns directly onto electrically insulated and platinized components. This automated technique is shown to produce gauges of high geometrical tolerance at precisely known locations, and to create arrays of gauges on the experimental components rapidly. Typically, the platinum resistance elements are 1 mm by 0.08 mm in plan form and have closely repeatable characteristics (for example, resistance and temperature coefficient). A novel technique for measuring the adiabatic wall temperature and heat transfer coefficient in short-duration facilities is also presented; this includes the capability to measure the deterministic component of these unsteady parameters in periodic (pulsating) flows. The combination of the new high spatial density gauge arrays and the capability to measure unsteady adiabatic wall temperature allows unprecedented insight into the flow physics that influences the unsteady heat flux. In particular, it has been possible to establish whether heat transfer rate fluctuations in a turbine experiment are caused by changes in flow recovery temperature or by changes in heat transfer coefficient. Some example measurements taken in a high-speed turbine test facility are described. Finally, some of the recently manufactured heat transfer gauge systems are presented.

Interaction between Wind and Temperature Fields in the Planetary Boundary Layer for a Spatially Heterogeneous Surface Heat Flux

Interaction between wind and temperature fields in the planetary boundary layerfor a spatially heterogeneous surface heat flux has been investigated using large-eddysimulation. It is shown that a substantial difference exists in the wind and temperaturefields, depending on whether the directions of the background wind and the surfaceheat flux variation are parallel or perpendicular. When they are parallel to each other, two-dimensional plumes induced by theheterogeneous surface heat flux are easily destroyed by the background wind,and the velocity field is strongly modified by convective eddies compared tothe case when they are perpendicular to each other. This leads to a substantialdifference in the profiles of turbulent kinetic energy and its flux. It also results in a difference between the two cases in the bulk properties of theplanetary boundary layer, such as the entrainment at the top of the planetary boundarylayer and the drag at the bottom, which have important implications for boundary-layermodelling. The difference between the two cases exists even when the background windspeed is as large as 15.0 m s-1. Meanwhile, the contrast between two cases is weakened by the Coriolis force.

Spatially Resolved Surface Heat Transfer for Parallel Rib Turbulators With 45 Deg Orientations Including Test Surface Conduction Analysis

Spatially resolved Nusselt numbers, spatially-averaged Nusselt numbers, and friction factors are presented for a stationary channel with an aspect ratio of 4 and angled rib turbulators inclined at 45 deg with parallel orientations on two opposite surfaces. Results are given at different Reynolds numbers based on channel height from 9000 to 76,000. The ratio of rib height to hydraulic diameter is 0.078, the rib pitch-to-height ratio is 10, and the blockage provided by the ribs is 25 percent of the channel cross-sectional area. Nusselt numbers are determined with three-dimensional conduction considered within the acrylic test surface. Test surface conduction results in important variations of surface heat flux, which give decreased local Nusselt number ratios near corners, where each rib joins the flat part of the test surface, and along the central part of each rib top surface. However, even with test surface conduction included in the analysis, spatially-resolved local Nusselt numbers are highest on tops of the rib turbulators, with lower magnitudes on flat surfaces between the ribs, where regions of flow separation and shear layer re-attachment have pronounced influences on local surface heat transfer behavior. The augmented local and spatially averaged Nusselt number ratios (rib turbulator Nusselt numbers normalized by values measured in a smooth channel) decrease on the rib tops, and on the flat regions away from the ribs, especially at locations just downstream of the ribs, as Reynolds number increases. With conduction along and within the test surface considered, globally averaged Nusselt number ratios vary from 3.53 to 1.79 as Reynolds number increases from 9000 to 76,000. Corresponding thermal performance parameters also decrease as Reynolds number increases over this range.

Simulated impact of intraseasonal variations in surface heat and momentum fluxes on the pelagic ecosystem of the Arabian Sea

A series of numerical experiments using a three‐dimensional, coupled ecosystem‐circulation model has been performed to evaluate the impact of variations on an “intraseasonal” daily to monthly timescale in surface fluxes of heat and momentum on simulated biological production in the Arabian Sea. The biological component is a four‐compartment, nitrogen‐based system; the physical component is a high‐vertical‐resolution z‐level model that includes a mixed‐layer model based on the turbulent energy equation and contrasts with layer models which often overestimate vertical mixing associated with intraseasonal mixed‐layer retreat and formation. Experiments show that the intraseasonal variations in the forcing may have to be considered when comparing sparsely sampled data with results from a numerical model. The experiments provide, however, no evidence that there is any rectification impact on longer timescales. In particular, accounting for intraseasonal variations has essentially no effect on the simulated annual mean biological production.

Large Eddy Simulation of Thermally Induced Oscillations in the Convective Boundary Layer

Mesoscale circulations induced by differential boundary layer heating due to surface inhomogeneities on scales of 5 km and more can significantly change the average properties and the structure of the convective boundary layer (CBL) as well as trigger off temporal oscillations. The results of one of the first numerical case studies using large eddy simulation (LES) on the mesoscale suggest that mesoscale circulations exhibit a considerably larger average kinetic energy than convection under homogeneous conditions. This affects turbulent transport processes and should be accounted for in larger-scale models even if their turbulence parameterizations rely on homogeneous control runs of high-resolution models. This case study uses the Hannover parallelized large eddy simulation model (PALM) with prescribed 1D sinusoidal surface heat flux variations on wavelengths from 2.5 to 40 km. The resulting mesoscale circulations are analyzed by means of domain-averaged cross sections, time averaged and normalized with the boundary layer height, as well as power spectra and domain-averaged time series. The simulated mesoscale circulations were periodic. Vertical profiles and time series demonstrate that the onset of the mesoscale circulation triggers off a temporal boundary layer oscillation, whose period and amplitude depend on the surface heat flux perturbation wavelength and amplitude and on the background wind component perpendicular to the surface inhomogeneity orientation. Spectral analysis shows that the mesoscale circulations damp convection equally in all directions. A hypothesis of the oscillation mechanism is briefly discussed.

Indonesian Rainfall Variability: Impacts of ENSO and Local Air–Sea Interaction

Relationships between Indonesian rainfall and Indo-Pacific sea surface temperatures (SSTs) and circulation anomalies are investigated using observations for 1951-97. Indonesia receives significant rainfall year-round but experiences a wet season that peaks in January and a dry season that peaks in August. Dry season rainfall anomalies are spatially coherent, strongly correlated with SST, and tightly coupled to El Nino-Southern Oscil- lation (ENSO) variations in the Pacific basin. Drought conditions typically occur during El Nino, when SSTs surrounding Indonesia are cool and the Walker circulation is weakened, resulting in anomalous surface easterlies across Indonesia. The opposite tends to occur during La Nina. Broadscale Indonesian rainfall and SST anomalies tend to not persist from the dry season into the wet season. Rainfall in the heart of the wet season tends to be uncorrelated with SST and spatially incoherent. Seasonally varying feedback between Indonesian SST, winds, and rainfall explains the growth, persistence, and coherence of the local anomalies during the dry season and their decay or change in sign once the wet season commences. During the dry season anomalous surface easterlies, remotely driven by warm SSTs in the central Pacific during El Nino, act to increase local wind speed, cooling the ocean surrounding and to the east of Indonesia and thereby increasing the anomalous SST gradient across the Pacific. Hence, local rainfall and the Walker circulation are further reduced. Once the wet season commences and the climatological surface winds across Indonesia shift from southeasterly to northwesterly, the anomalous surface easterlies now act to reduce the wind speed. The initial cold SST anomaly is damped, reducing the negative rainfall anomalies and surface easterlies. The opposite scenario occurs during La Nina. Indonesian rainfall variations during the dry season are also coupled to the development of an anomalous zonal SST gradient in the equatorial Indian Ocean. This anomalous gradient is strongly related to ENSO and is most prominent during the dry season. Once the wet season commences, the entire Indian Ocean tends to have the same-signed SST anomaly (positive during El Nino and negative during La Nina). Development and decay of this anomalous zonal SST gradient in the Indian Ocean is promoted by seasonally varying air-sea interaction in the eastern Indian Ocean in response to ENSO conditions in the Pacific. The eastern Indian Ocean SST changes are driven largely by induced surface heat flux variations (primarily changes in latent heat flux and net shortwave radiation). Biennial variations in the Indonesian region may also be induced by this seasonally varying air-sea interaction associated with ENSO.

Measurement of Air–Sea Fluxes over the Indian Ocean and the Bay of Bengal

Atmospheric and oceanic data were collected in 1998 and 1999 over the tropical Indian Ocean during three cruises of the Indian research vessel Sagar Kanya, covering different geographic locations and seasons, including boreal winter, peak monsoon, and postmonsoon periods. The present study is mainly based on the measurements made during the three cruises. It is found that there are important differences in the near-surface characteristics during monsoon and other seasons. The largest variations in the net surface heat flux occurred during the monsoon period. The specific humidity difference between sea surface and air at 10-m height shows a strong seasonal dependence, with the lowest values observed during the monsoon period. An important finding from the ship observations is that, at a given SST, the surface air over the Indian Ocean is much warmer compared to that over other tropical oceans and the west Pacific warm pool in particular. These findings are supported by data obtained by a moored buoy in the north Indian Ocean and also from the Comprehensive Ocean-Atmosphere Data Set for the Indian Ocean.

Micrometeorological modeling to understand the thermal anomaly in the sand dunes across the Israel–Egypt border

A thermal anomaly was observed on the remote sensing images in the sand dunes across the Israel–Egypt border. The Israeli side with more vegetation cover has higher (>2°C) land surface temperature (LST) during the day than the Egyptian side where bare sand prevails. This anomaly is very obvious at about noon in the hot dry summer season. A micrometeorological model has been established in terms of surface energy balance for simulating the surface temperature change and heat flux variation of the region. The purpose of this modeling is to understand the mechanism leading to the occurrence of the thermal anomaly and to reveal the key factors controlling the surface temperature change. The characteristic of the model lies in its coupling soil temperature changing simultaneously with soil moisture movement, described as two differential equations. The methodology for the numerical solution of the model has been developed. The required meteorological data and soil parameters were measured at the study region in the hot summer season for the simulation. Two typical and the most important surface patterns of the region are considered: biogenic crust representing the Israeli side and the bare sand representing the Egyptian side. Results from simulation indicate that surface albedo contributes most to the surface temperature difference between the two typical surfaces, which is followed by sub-soil properties (mainly soil moisture) difference. Biogenic crust has lower surface albedo than bare sand. Consequently, it absorbs much more incident sky radiation. During the hot summer season, the region is very dry and vegetation is in dormancy. The canopy of most shrubs reduces to minimum. Even though the Israeli side has more vegetation, the evapo-transpiration contributed by the vegetation is still very small (<7%) in comparison with the net radiation. This small latent heat flux has little effect on the surface energy balance process in the arid environment. LST change in the desert region is mainly controlled by the amount of incident solar energy absorbed by the ground as soil heat. Therefore, the anomalous LST change and thermal variation on both sides of the region can still be explained as the direct result of the obvious albedo difference on both sides. This albedo difference is mainly caused by the sharp contrast of surface composition especially different biogenic crust and bare sand cover rates on both sides. The overgrazing and other anthropogenic stresses are the direct reasons leading to the bare sand (high albedo) prevalent on the Egyptian side while the conservation policy helps the development of biogenic crust and vegetation (low albedo) on the Israeli side.

Variations of Sensible and Latent Heat Fluxes from a Great Lakes Buoy and Associated Synoptic Weather Patterns

An investigation of sensible and latent heat fluxes and their relation to synoptic weather events was performed using hourly meteorological measurements from National Data Buoy Center buoy 45003, located in northern Lake Huron, during April‐November of 1984. Two temporal heat flux regimes were found to exist over Lake Huron. The first period extended from April through July and was characterized by periods of modest negative (downward) heat fluxes. The second regime was marked by periods of large positive (upward) heat fluxes and occurred from August through November. This later period accounted for 95%‐100% of both the total positive sensible and latent heat fluxes. In addition, a comparison of the seasonal evolution of sensible and latent heat fluxes showed the transition from the negative to the positive flux regime occurred 10‐20 days earlier for latent heat flux than for sensible heat flux. A notable, statistically significant increase of the surface heat flux variability from the negative to positive flux regimes with a general decrease in the near-surface atmospheric stability during the positive flux regime was found. During both flux regimes, the magnitude of surface sensible and latent heat fluxes remained coupled to transient synoptic-scale weather events. On average, the occurrences of minimum (maximum) heat fluxes preceded time periods of low (high) sea level pressure by 0‐3 h during the negative flux regime. For the positive flux regime, maximum (minimum) surface heat fluxes followed the passage of low (high) pressure by approximately 24 h. In addition, maximum (minimum) sensible and latent heat fluxes preceded synoptic high (low) pressure by approximately 16 h. Typical synoptic surface weather patterns were identified for both significant positive and negative heat flux events, time periods when the atmosphere‐lake heat exchange was maximized.

LARGE-EDDY SIMULATION OF THERMALLY INDUCED OSCILLATIONS IN THE CONVECTIVE BOUNDARY LAYER

Abstract Mesoscale circulations induced by differential boundary layer heating due to surface inhomogeneities on scales of 5 km and more can significantly change the average properties and the structure of the convective boundary layer (CBL) as well as trigger off temporal oscillations. The results of one of the first numerical case studies using large eddy simulation (LES) on the mesoscale suggest that mesoscale circulations exhibit a considerably larger average kinetic energy than convection under homogeneous conditions. This affects turbulent transport processes and should be accounted for in larger-scale models even if their turbulence parameterizations rely on homogeneous control runs of high-resolution models. This case study uses the Hannover parallelized large eddy simulation model (PALM) with prescribed 1D sinusoidal surface heat flux variations on wavelengths from 2.5 to 40 km. The resulting mesoscale circulations are analyzed by means of domain-averaged cross sections, time averaged and normali...

Convection in Io's asthenosphere: Redistribution of nonuniform tidal heating by mean flows

Numerical simulations of convection in a wide domain with spatially varying internal heating intended to mimic tidal dissipation in Io's proposed asthenosphere are performed in order to better understand the convective dynamics and, in particular, to quantify the relationship between surface observables (particularly the distribution of heat flux) and tidal dissipation. Two‐dimensional calculations at high internal heating Rayleigh number RaQ of up to 1010 indicate a mean, domain‐wide flow with superimposed small‐scale instabilities. The mean flow spreads out the tidally‐dissipated heat, resulting in long‐wavelength surface heat flux variations that decrease in proportion to RaQ−0.21.. This scaling is shown to apply to different domain widths and also to three‐dimensional geometry. Powerlaw scalings are also obtained for velocities and temperatures. These mean flow scalings are also derived analytically. Scaling to Io's asthenosphere, long‐wavelength heat flux variations of order several percent are predicted, with temperature variations of order tens of Kelvins and mean flow velocities of 50–5600 m.yr−1.

Impacts of Diurnal Cycle of SST on the Intraseasonal Variation of Surface Heat Flux over the Western Pacific Warm Pool

Based on the method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of daily averaged wind speed, precipitation and peak surface radiation, a parameterization scheme of diurnal cycle of SST is developed in the present study, Integrations to National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3), separately forced by observed weekly SSTs with and without diurnal cycle of SST, are compared. Surface observation obtained from the Improved Meteorology (IMET) buoy during TOGA COARE Intensive Observation Period is applied to verify the SST parameterization, as well as a validation to the results from the CCM3 simulation. It is shown that the superposition of diurnal cycle of SST to the forced weekly SST makes a more realistic representation of the surface structure of intraseasonal oscillation over the western Pacific warm pool.

A New Model of the Madden–Julian Oscillation

A new model of the Madden–Julian oscillation (MJO) is presented. Cloud–radiation interactions in this model make the tropical atmosphere susceptible to large-scale radiative–convective overturning. The modeled MJO takes the form of such an instability, though its behavior is substantially modified by the effects of surface heat flux variability. The dynamics of the disturbance in the model are quasi-balanced, in the sense that the low-level flow in the disturbance is more associated with the vorticity than with the divergence. The cumulus parameterization used in the model allows a lag of several days to exist between the strongest surface heat flux into a column and the development of heavy precipitation in that column. This lag plays a key role in model dynamics.

Observations of Systematic Boundary Layer Divergence Patterns and Their Relationship to Land Use and Topography

Abstract Data from several surface meteorological networks in the vicinity of the U.S. Department of Energy’s Southern Great Plains Cloud and Radiation Testbed were used to investigate the relationship between boundary layer circulations, as reflected in composited divergence fields, and variations in vegetation, surface temperature, and topography. The study is unique in using data from a dense collection of surface meteorological instruments that are distributed over a region comparable in size to a GCM grid cell in a region of sharply varying land use. These land use differences provide variations in surface heat flux on a scale O(100 km) that has been postulated to produce the strongest surface-induced mesoscale circulations in the boundary layer. This paper details the first signature in data of a boundary layer circulation that can be attributed to land use differences at this scale. It is found, however, that in the composited fields the majority of the divergence extrema persist over seasons, are ...

Looking for the Role of the Ocean in Tropical Atlantic Decadal Climate Variability*

Abstract Ocean models are used to investigate how variations in surface heat fluxes and ocean heat transports contribute to variations of tropical Atlantic SSTs on decadal timescales. The observed patterns of variability, deduced from reanalyses of the National Centers for Environmental Prediction (NCEP), are found to involve the ocean’s response to variations in the strength of the northeast and southeast trades. Stronger trade winds are associated with anomalously cool surface temperatures. The trade winds and surface temperatures in each hemisphere appear to behave independently but each is associated with anomalous cross-equatorial flow. A numerical model is used in an attempt to simulate this variability. The model is an ocean general circulation model coupled to a simple model of the atmospheric mixed layer and is forced by NCEP winds from 1958 to 1998. The model reasonably reproduces the observed variability. Analysis of the ocean model’s mixed layer energy budget shows that, on decadal timescales,...

Radioactive heat generation and its thermal effects in the Alps–Apennines boundary zone

Radioactive heat-production data of rocks cropping out at the Alps–Apennines boundary zone (NW Italy) are presented. Samples were analysed in the laboratory by means of a gamma-ray spectrometer. They are representative of the Savona Unit and the ophiolitic sequences, with metasediments and sediments, of the Voltri Massif, the Sestri-Voltaggio Zone and the Lavagna Nappe. The heat-production rate of sedimentary rocks ranges from 1.05 (limestones) to 2.52μWm−3 (shales). In ophiolites, it varies from 0.04 (serpentinites) to 0.24μWm−3 (metabasalts). Orthogneisses of the Savona Unit show the highest value (2.92μWm−3). Potassium contributes to the heat generation on average by 17%. In the metasedimentary and sedimentary rocks, thorium contribution accounts on average by 43%, except for dolomites in which 97% of the radioactive heat is produced by uranium. Calc-schists, shales, radiolarites and phyllites give a Th/U ratio ranging from 3 to 4, that is very close to that of orthogneisses. This ratio is lower in limestones, almost all ophiolites and dolomites. Most rocks show a K/Th ratio ranging between 2×103 and 4×103. These data together with available thermal conductivity information are used in a finite element simulation to analyse the effects on the heat flux and temperature distribution due to lateral variation of thermal parameters. Changes in structure and composition of the uppermost part of the crust result in small wavelength variation of surface heat flux. The low radioactive heat production of ophiolites produces a decrease of about 10mWm−2 in the surface heat-flux on the Voltri Massif.

Coupling an Advanced Land Surface–Hydrology Model with the Penn State–NCAR MM5 Modeling System. Part I: Model Implementation and Sensitivity

This paper addresses and documents a number of issues related to the implementation of an advanced land surface–hydrology model in the Penn State–NCAR fifth-generation Mesoscale Model (MM5). The concept adopted here is that the land surface model should be able to provide not only reasonable diurnal variations of surface heat fluxes as surface boundary conditions for coupled models, but also correct seasonal evolutions of soil moisture in the context of a long-term data assimilation system. In a similar way to that in which the modified Oregon State University land surface model (LSM) has been used in the NCEP global and regional forecast models, it is implemented in MM5 to facilitate the initialization of soil moisture. Also, 1-km resolution vegetation and soil texture maps are introduced in the coupled MM5–LSM system to help identify vegetation/water/soil characteristics at fine scales and capture the feedback of these land surface forcings. A monthly varying climatological 0.15° × 0.15° green vegetation fraction is utilized to represent the annual control of vegetation on the surface evaporation. Specification of various vegetation and soil parameters is discussed, and the available water capacity in the LSM is extended to account for subgrid-scale heterogeneity. The coupling of the LSM to MM5 is also sensitive to the treatment of the surface layer, especially the calculation of the roughness length for heat/moisture. Including the effect of the molecular sublayer can improve the simulation of surface heat flux. It is shown that the soil thermal and hydraulic conductivities and the surface energy balance are very sensitive to soil moisture changes. Hence, it is necessary to establish an appropriate soil moisture data assimilation system to improve the soil moisture initialization at fine scales.