Micrometeorological Parameters Research Articles

Seasonal trends and spatial variations of PM10-bounded polycyclic aromatic hydrocarbons in Veneto Region, Northeast Italy

The Veneto Region extends for ∼18.4·103 km2 in the northeastern part of the Po Valley and includes mountains, hills, plain and coastal environments with very different and discontinuous anthropogenic pressures. Although many efforts have been made to mitigate air pollution, the European air quality standards for atmospheric pollutants are frequently breached. This study investigates the levels of eight PM10-bound PAHs collected in 21 stations categorized as rural background, urban and suburban backgrounds, traffic and industrial hot-spots during one year (2011). Data were statistically processed to detect the PAH seasonal trends, their relationship with other air pollutants and micro-meteorological parameters and the space variations at a regional scale. Results show that PAHs levels are relatively high in the largest part of the region, with 10 sites exceeding the levels of BaP targeted by the European legislation. Two sites exhibited anomalously high PAHs concentrations and this anomaly became even more evident when considering the population density as a surrogate for the potential anthropogenic pressure. The PAHs levels were found directly proportional to other gaseous pollutants (CO, NO, NOx, SO2) suggesting common polluting sources. The analysis of time trends of PAH concentrations reveals significant coincidences throughout the region, i.e. simultaneous changes are observed in most sites as a consequence of similar emission sources and accumulation/removal processes. In this scenario, the control strategies currently imposed at local level (e.g. traffic limitations) have proven scarcely effective in mitigating air pollution and a real coordination at regional or even interregional level cannot be further postponed. Peculiar features of the PAHs pollution in the Veneto were also identified and some measures for protecting the human health were suggested.

Soil erosion by wind over tilled surfaces in South Tunisia

Wind erosion flux measurements and associated micrometeorological parameters were obtained in South Tunisia over agricultural plots that have been tilled with different ploughing tools (mouldboard, tiller, disc). Complementary measurements were also performed to characterize the surface properties, especially the geometric characteristics of the ridges and the soil grain size distribution.The results clearly show that the wind erosion fluxes are significantly higher over agricultural surfaces tilled by disc plough compared to those measured on the plot tilled with mouldboard or tiller ploughs. The difference in the erosion fluxes is about a factor 4 between disc and tiller and an order of magnitude between disc and mouldboard. These results strongly suggest that the new techniques of tillage, like disc, could increase drastically the soil erosion by wind, at least on agricultural plots constituted of loose soils.These results were also used to test the parameterization proposed by Kardous et al. (2005a,b) to simulate the horizontal fluxes of sediment produced by wind over ridged surfaces. The comparisons between the simulations performed by using this parameterization and the measured erosion fluxes show that this parameterization, despite its simplicity, reproduces quite satisfyingly the measurements whatever the type of surfaces and for both low and intense erosion events. However, sensitivity tests have pointed out that this parameterization is especially sensitive to the precision at which the geometric characteristics of the ridges are determined.

Open Top Chambers and Infrared Lamps: A Comparison of Heating Efficacy and CO2/CH4 Dynamics in a Northern Michigan Peatland

Open top chambers (OTCs) and infrared (IR) lamps have been widely used for experimentally warming ecosystems, especially in high latitude and alpine regions. The efficacy of OTCs and IR lamps is variable, yet there has not been a direct, experimentally controlled comparison of these warming methods. We, therefore, implemented a factorial study in a northern Michigan peatland to test how warming and microtopography interacted to affect micrometeorological parameters and CO2 and CH4 flux rates. IR lamps significantly warmed the soil (5 cm depth; P < 0.05) by 1.4 and 1.9°C in 2009 and 2010, respectively, with the majority of warming occurring during nighttime hours. OTCs did not provide any long-term warming increase compared to control plots, which is contrary to OTC studies at high latitudes. By investigating diurnal heating patterns and micrometeorological variables, we determined that OTCs were not achieving strong daytime heating peaks and were often cooler than controls during nighttime hours. Temperate day-length, cloudy and humid conditions, and latent heat loss were factors that may have inhibited OTC warming. Warming treatments created mixed effects on gas flux components. Within drier, hummock plots, IR lamps significantly increased gross ecosystem production (GEP) but not ecosystem respiration (ER), whereas OTCs had no effect on GEP or ER in hummocks. In wetter, lawn plots, warming treatments had no effect on CO2 flux or CH4 flux. We show here that IR lamps are more effective than OTCs for studying how temperate peatlands may respond to increased temperatures.

Unexpected absence of control of rubber tree growth by soil water shortage in dry subhumid climate

Rubber tree cultivation is presently expanding rapidly into dry subhumid areas. As a consequence, trees face a long dry season. Low growth rates are delaying the start of tapping. The relationship between the growth rate and the soil water availability is not clear. Therefore, we studied the origin of low growth rates. For that we analyzed the relationships between growth, plant water stress, and soil water availability along a toposequence with a soil depth gradient. The plantation of 3-year-old Hevea brasiliensis trees was located in northeast Thailand. Tree circumference, predawn leaf water potential (p), soil water potential (s), and micrometeorological parameters were monitored from 2007 to 2010. Results show spatial and temporal variability of growth with a threshold value of leaf water potential of −0.4 MPa for growth. This leaf water potential threshold was not associated with very dry soils as soil water potentials were higher than −0.05 Mpa. But the leaf water potential threshold was associated with a high air vapor pressure deficit higher than 3–4 kPa. Leaf water potential decreased when the soil at the bottom of the slope was saturated in the rainy season. These results provide, for the first time, evidence that soil water shortage is unexpectedly not the main cause of low growth rates. Dry air in the dry season and waterlogging in rainy season are major constraints.

Characterisation of PM2.5 concentrations and turbulent fluxes on a island of the Venice lagoon using high temporal resolution measurements

This work presents an analysis of PM2.5 concentrations and vertical turbulent fluxes on an island of the Venice lagoon. Data were collected during three measurement campaigns in spring, summer and winter periods. Measurements were taken with a high-resolution optical PM2.5 detector, coupled with a micrometeorological station that allowed the evaluation of the vertical turbulent fluxes of PM2.5 using the eddy-correlation technique. The main objective of this paper is to analyse the daily and seasonal pattern in PM2.5 concentrations and fluxes and to discuss their correlation with the main meteorological and micrometeorological parameters using high temporal resolution measurements. Observed data showed a seasonal pattern in turbulent fluxes with daytime average positive value during winter and negative during summer. Deposition velocities, ranged from –60 to 20 mm/s, appeared to be mainly influenced by atmospheric stability. There were larger emissions in cases of high wind velocities blowing from water sector indicating a significant potential contribution of sea spray to PM2.5 fluxes. The local atmospheric circulation, due to the orography of the area, was characterised by diurnal winds coming from the Adriatic Sea and nocturnal wind coming from the Alps. This circulation influenced deposition velocity creating an increase of negative fluxes in the morning at the starting of the sea breeze. A diurnal pattern in concentration has been observed and it is similar for all three measurement campaigns, with higher concentrations in nocturnal periods. The daily pattern was investigated in terms of its correlation with meteorological and micro-meteorological parameters, and was found highly correlated with the diurnal pattern of boundary layer height (BLH) and with relative humidity.

Influence of Canopy Management Practices on Vineyard Microclimate: Definition of New Microclimatic Indices

Meteorological parameters have a crucial influence on grapevine ( Vitis vinifera L.) production quantity and quality. Most of the commonly used bioclimatic indices are not appropriate to represent intravineyard micrometeorological variability, in particular the subdaily dynamics that are important in grape maturation processes. The aim of this research was to compile a new set of micrometeorological indices and evaluate their capacity to discriminate the differences in the microclimatic daily cycle induced by different canopy management techniques, based on a statistical data set of three years (2008, 2009, 2010) of hourly data of cluster internal temperature, canopy air temperature, and solar radiation intercepted by the cluster. Data was collected in four vineyards planted with Sangiovese and Cabernet Sauvignon, located in three climatic zones of Tuscany (Italy). Starting from this data set, some new micrometeorological indices were defined using two different criteria for subdaily time segmentation: static, based on fixed hourly intervals, and dynamic, based on solar height daytime segmentation. Results showed that indices based on subdaily data better provide a better representation of vineyard microclimate than daily indices and are able to highlight microclimatic differences induced by canopy management practices. The indices more sensitive to treatments are those related to the solar radiation intercepted by the cluster parameter and relative to the Broad Daylight Index, which represent the average of micrometeorological parameters in the middle hours of the day. The proposed indices enhance the characterization of micrometeorological conditions induced by different canopy management practices and, therefore, the assessment of the within-vineyard spatial variability of environmental parameters.

Micrometeorological dynamics within mustard (Brassica juncea) crop canopy under semi-arid conditions of northern India

Field experiments were conducted for two years (2005-06 and 2006-07) at IARI, New Delhi, India research farm to assess the variations of micrometeorological parameters under differential hydrothermal regimes in mustard crop. Changes in sowing time and branch removal/defoliation treatments were imposed in order to create variations in hydrothermal regimes under phenology based irrigation scheduling. It was inferred that near-ground surfaces in the debranched plot where microenvironment was modified, air temperatures were higher (2 to 3 0C) as compared to control plots, decreased at 35 cm and remained almost similar with further increase in height at 1130 hrs while at 1430 hrs the magnitude of temperature variations was relatively higher. In contrast to air temperature, the relative humidity in debranched plot was less than that of the control plot. At near-ground, even at higher canopy height about 10% higher RH variations were observed in control plot as compared to debranched plot both in morning and afternoon hours. Furthermore, leaf area index could explain variations in temperature and RH to the tune of 40-50%. Radiation penetration and soil moisture depletion pattern also indicated significant impact of microclimatic variations near the ground.

Coupling soil-vegetationatmosphere- transfer model with energy balance model for estimating energy and water vapor fluxes over an olive grove in a semi-arid region

Simple soil-vegetation-transfer (SVAT) and energy balance models were used to estimate the surface turbulent fluxes (&lt;em&gt;i.e. &lt;/em&gt;sensible and latent heat fluxes) over a complex olive grove using thermal infra-red surface temperature (TIRST). This approach used a dual source SVAT model to calculate the sensible heat fluxes from radiometric surface temperature. These fluxes were then used together with the estimates of the available energy also derived from TIRST to estimate the latent heat flux by applying the first law of thermodynamics &lt;em&gt;i.e.&lt;/em&gt; the conservation of energy principle. The data used to validate this approach were collected over an irrigated olive grove site located in central Morocco near Marrakech. Mass and energy fluxes, as well as micrometeorological parameters, were continuously measured during the year 2003. The comparison between estimated and measured daily sensible heat fluxes yielded an acceptable agreement in spite of the complexity of the study surface with a correlation coefficient (R&lt;sup&gt;2&lt;/sup&gt;=0.86) and root mean square error (RMSE) of 28 Wm&lt;sup&gt;-2&lt;/sup&gt;. For the latent heat fluxes, the statistical result for the comparison between estimated and measured daily values showed a larger scatter than that revealed for the sensible heat fluxes (R&lt;sup&gt;2&lt;/sup&gt;=0.75; RMSE=31.42 Wm&lt;sup&gt;-2&lt;/sup&gt;). However, the correspondence is to be considered acceptable given the difficulty in estimating latent heat flux over such a complex field. Therefore, it can be concluded that, in spite of the simplicity of the proposed approach, it can be considered a suitable tool for estimating the turbulent fluxes using TIRST over complex surfaces.

Analysis of particles and carbon dioxide concentrations and fluxes in an urban area: Correlation with traffic rate and local micrometeorology

Abstract Number particle concentrations and fluxes were measured, synchronously with CO2 concentrations and fluxes, in an urban area. Measurements were taken with an eddy-correlation station located near the busiest road of the town of Lecce (Italy). Upward fluxes dominate completely over deposition and the area behaved as a source of aerosol and CO2 with an average particle flux FN = 71,100 #/cm2 s (median 64,000 #/cm2 s) and an average CO2 flux FC = 0.76 mg/m2 s (median 0.46 mg/m2 s). Pronounced diurnal and weekly cycles of FN and FC were observed, well correlated with measured traffic rate, TR, indicating that traffic is the main source of CO2 and particles in the area. Biogenic cycle on CO2 fluxes and concentrations was also distinguishable, decreasing the correlation between FN and FC. The relationships between particle and CO2 fluxes with TR, friction velocity and atmospheric stability were analysed. Measured FN/TR increased when friction velocity increased and, correspondingly, number concentration decreased. Particle fluxes showed a dependence on the atmospheric stability. These dependencies were used to derive an empirical parameterisation of aerosol concentration and fluxes, based on TR and micrometeorological parameters, that could be used to estimate traffic emissions, in real operating conditions, for applications in dispersion and climate modelling. Measured FC/TR showed a limited correlation with friction velocity and stability, because of the influence of the biogenic cycle, thereby micrometeorological parameters were not used in the parameterisation of FC.

Unusual diurnal variation in surface ozone observed after the 26 December 2004 tsunami over the rural site of Bay of Bengal, India

Measurements of surface ozone (O3) and nitrogen dioxide (NO2) were studied from December 2004 to February 2005, covering the giant tsunami event on 26 December 2004 at Tranquebar (11° N, 79.9° E, 9 m) over the west coast of the Bay of Bengal, India. An unusual maximum O3 concentration of 28 parts per billion by volume (ppbv) was observed in the morning and a minimum (16 ppbv) in the evening, indicating that pronounced chemical loss of O3 occurred in the daytime after the tsunami over this coastal region. An increase in NO2 concentration from 5.6 ppbv before the tsunami to 10.5 ppbv after the tsunami was observed in the daytime. The observed unusual diurnal changes in O3 were not due to mass transport processes as the five-day back trajectories of air parcels transport before and after the tsunami remained unchanged. Similarly, meteorological and micrometeorological parameters were found to be normal before and after the tsunami. The unusual low O3 level during the daytime was possibly due to prolonged excess emission of iodocarbons from the sea surface after the tsunami, which resulted in enhanced inorganic iodine (I x ) concentration, leading to massive destruction of O3. Similarly, unusually high O3 levels during the night-time were possibly due to the intrusion of ozone-rich air after the tsunami from the free troposphere into the surface layer when the boundary layer height shrinks after midnight. The present work can be extended on a regional scale by incorporating modelling studies using recent remote sensing tools.

Micrometeorological observations above a Japanese red pine forest within the growing season

Knowledge of vegetation-atmosphere interactions has great importance in ecological research, and to recognize these effective interactions, the collection and interpretation of micrometeorological data are essential. The main goal of this study was to understand the trends of evapotranspiration (ET) and other micrometeorological parameters within the growing season above a Japanese red pine forest in Japan. To measure ET, the Bowen ratio-energy balance approach was employed. These measurements were used with the Penman-Monteith reference evapotranspiration (ET_0) in order to create crop coefficients (K_c) by the ratio of ET:ET_0. Mean daily ET on the dry and rainy days was found to be 3.22 and 2.11 mm day^{-1}, respectively, which was statistically different. K_c values were inconsistent from day to day and ranged between 0.37 and 1.24, and, in general, were less than unity (average: 0.84, standard error: 0.01). Significant differences in K_c were found between rainy days (wet canopy) and dry days (dry canopy). No remarkable changes were observed between rainy and dry days in the average contribution of latent heat flux, ground heat flux, and sensible heat flux to the energy budget. The data indicated that the Penman-Monteith equation may be useful for estimating the ET from the red pine forest within the growing season, and, in particular, when the rainy and dry days were separated.

On the new parameterisation of the eddy diffusivity for radioactive pollutant dispersion

In the present work, starting from the evolution equation for the turbulent energy density spectrum, we develop a new model for the growth of the turbulence in convective boundary layer. We apply dimensional analysis to parameterise the unknown inertial transport and convective source term in the dynamic equation for the three-dimensional spectrum. The non-linear integrodifferential equation is solved by Adomian decomposition method. Using the micrometeorological parameters generated by large eddy simulation, for the first time, we employ the vertical component of the energy spectrum to calculate the eddy diffusivity (required in dispersion models). This new eddy diffusivity is used in the GILTT approach to simulate ground-level concentrations considering experimental data of Angra I Nuclear Power Plant.

On the dynamics of canopy resistance: Generalized linear estimation and relationships with primary micrometeorological variables

The 1‐D and single layer combination‐based energy balance Penman‐Monteith (PM) model has limitations in practical application due to the lack of canopy resistance (rc) data for different vegetation surfaces. rc could be estimated by inversion of the PM model if the actual evapotranspiration (ETa) rate is known, but this approach has its own set of issues. Instead, an empirical method of estimating rc is suggested in this study. We investigated the relationships between primary micrometeorological parameters and rc and developed seven models to estimate rc for a nonstressed maize canopy on an hourly time step using a generalized‐linear modeling approach. The most complex rc model uses net radiation (Rn), air temperature (Ta), vapor pressure deficit (VPD), relative humidity (RH), wind speed at 3 m (u3), aerodynamic resistance (ra), leaf area index (LAI), and solar zenith angle (Θ). The simplest model requires Rn, Ta, and RH. We present the practical implementation of all models via experimental validation using scaled up rc data obtained from the dynamic diffusion porometer‐measured leaf stomatal resistance through an extensive field campaign in 2006. For further validation, we estimated ETa by solving the PM model using the modeled rc from all seven models and compared the PM ETa estimates with the Bowen ratio energy balance system (BREBS)‐measured ETa for an independent data set in 2005. The relationships between hourly rc versus Ta, RH, VPD, Rn, incoming shortwave radiation (Rs), u3, wind direction, LAI, Θ, and ra were presented and discussed. We demonstrated the negative impact of exclusion of LAI when modeling rc, whereas exclusion of ra and Θ did not impact the performance of the rc models. Compared to the calibration results, the validation root mean square difference between observed and modeled rc increased by 5 s m−1 for all rc models developed, ranging from 9.9 s m−1 for the most complex model to 22.8 s m−1 for the simplest model, as compared with the observed rc. The validation r2 values were close to 0.70 for all models, and the modeling efficiency ranged from 0.61 for the most complex model to −1.09 for the simplest model. There was a strong agreement between the BREBS‐measured and the PM‐estimated ETa using modeled rc. These findings can aid in the selection of a suitable model based on the availability and quality of the input data to predict rc for one‐step application of the PM model to estimate ETa for a nonstressed maize canopy.

Coupling heat flux dynamics with meteorological conditions in the green roof ecosystem

Green roofs can notably modify the thermal properties of the building envelope and adjacent air to bring environmental benefits. This study investigates the heat flux dynamics of the tropical green roof ecosystem to provide a scientific basis for design and management. Green roof experimental plots were established to monitor the total solar radiation, net radiation, and micrometeorological parameters. The data permit calculation of sensible and latent heat fluxes using the Bowen ratio energy balance (BREB) method. The results demonstrated the life cycle characteristics of heat flux components. The dynamic changes of sensible ( H), latent ( λE) and soil ( G) heat fluxes were denoted by single-peak quadratic curves. Net radiation ( R n ) was largely determined by quantity and variation trends of λE, reaching at 1300 h a maximum λE of 655 W m −2 and maximum H of 369 W m −2. Temporal heat-flux fluctuations were strongly correlated with meteorological variables. Extreme values of H and λE correlated well with precipitation and temperature ( R 2 = 0.78). Dynamics of heat-flux magnitude and partitioning demonstrated notable differences by daily and season periods. They displayed considerable variations in flux partitioning, with Bowen ratios strongly correlated with weather conditions and vegetation types. The energy budget of the green roof ecosystem is unbalanced with a heat loss of about 15.5% caused by soil and canopy heat reserve. The passive indoor cooling effect under the green roof is attributed to the unbalanced energy closure.

Tritium dispersion simulation in the atmosphere by the integral transform technique using micrometeorological parameters generated by large eddy simulation

In this work, we report a numerical and statistical comparison between Advection-Diffusion Multilayer Method (ADMM) and Generalised Integral Laplace Transform Technique (GILTT) approaches to simulate a radioactive pollutant dispersion in the Atmospheric Boundary Layer (ABL) using micrometeorological parameters generated by Large Eddy Simulation (LES). To better describe the wind profile of the irregular ground level terrain, we considered the wind profile as a solution of the MesoNH model. We performed numerical simulations and comparisons against the data of Angra dos Reis-Brazil field experiments.

The Dome C site testing from an atmospheric physicist view

Atmospheric field experiments were made at the French-Italian station of Concordia at Dome C during several years. These experiments were limited to the summer season. In 2005 Concordia has become a permanent base, this allowed to carry out STABLEDC (STudy of the Atmospheric Boundary Layer Environmental at Dome C plateau station) that is an atmospheric field experiment of the duration of one year. The aim of STABLEDC was to study the processes occurring in the long-lived stable and the weak convective atmospheric boundary layers, observed during winter and summer, respectively, and to collect the relevant parameters for the atmospheric models. Both in situ and ground based remote sensing instruments have been used to monitor the meteorological parameters. The first part of the paper gives a brief illustration of the objectives of the field experiment, and a description of site and instrumentation. The second part shows the behaviour of some micrometeorological parameters: temperature, wind speed, sensible heat flux. The surface radiation balance components are also shown. Finally some experimental activities are proposed.

Characteristics of the boundary layerat Ny-Ålesund in the Arctic during the ARTIST field experiment

A preliminary analysis of boundary layer data acquired during the Arctic Radiation and Turbulence Interaction Study Experiment (ARTIST) at Ny-Alesund (Spitzbergen) in 1998 is presented. As expected, the wind fi eld and the thermal structure of the boundary layer are strongly infl uenced by the katabatic fl ow blowing along the Kongsfjorden. In particular, if the large scale circulation has a component along the same direction, the resulting low level wind reaches velocities comparable with geostrophic wind. Stable to neutral conditions occurred most of the time, sustaining inversion or spiky layers respectively, depending on the wind intensity. The behaviour of some micrometeorological parameters was examined in relation to the general fl ow pattern and the characteristics of this area. The highest values of surface sensible heat fl ux (with negative sign) were observed during daytime, in presence of forced convection, due to the transfer of warmer upper layer air into the surface layer.

Dynamics of ammonia exchange with cut grassland: synthesis of results and conclusions of the GRAMINAE Integrated Experiment

Abstract. Improved data on biosphere-atmosphere exchange are fundamental to understanding the production and fate of ammonia (NH3) in the atmosphere. The GRAMINAE Integrated Experiment combined novel measurement and modelling approaches to provide the most comprehensive analysis of the interactions to date. Major inter-comparisons of micrometeorological parameters and NH3 flux measurements using the aerodynamic gradient method and relaxed eddy accumulation (REA) were conducted. These showed close agreement, though the REA systems proved insufficiently precise to investigate vertical flux divergence. Grassland management had a large effect on fluxes: emissions increased after grass cutting (−50 to 700 ng m−2 s−1 NH3) and after N-fertilization (0 to 3800 ng m−2 s−1) compared with before the cut (−60 to 40 ng m−2 s−1). Effects of advection and air chemistry were investigated using horizontal NH3 profiles, acid gas and particle flux measurements. Inverse modelling of NH3 emission from an experimental farm agreed closely with inventory estimates, while advection errors were used to correct measured grassland fluxes. Advection effects were caused both by the farm and by emissions from the field, with an inverse dispersion-deposition model providing a reliable new approach to estimate net NH3 fluxes. Effects of aerosol chemistry on net NH3 fluxes were small, while the measurements allowed NH3-induced particle growth rates to be calculated and aerosol fluxes to be corrected. Bioassays estimated the emission potential Γ = [NH4+]/[H+] for different plant pools, with the apoplast having the smallest values (30–1000). The main within-canopy sources of NH3 emission appeared to be leaf litter and the soil surface, with Γ up to 3 million and 300 000, respectively. Cuvette and within-canopy analyses confirmed the role of leaf litter NH3 emission, which, prior to cutting, was mostly recaptured within the canopy. Measured ammonia fluxes were compared with three models: an ecosystem model (PaSim), a soil vegetation atmosphere transfer model (SURFATM-NH3) and a dynamic leaf chemistry model (DCC model). The different models each reproduced the main temporal dynamics in the flux, highlighting the importance of canopy temperature dynamics (Surfatm-NH3), interactions with ecosystem nitrogen cycling (PaSim) and the role of leaf surface chemistry (DCC model). Overall, net above-canopy fluxes were mostly determined by stomatal and cuticular uptake (before the cut), leaf litter emissions (after the cut) and fertilizer and litter emissions (after fertilization). The dynamics of ammonia emission from leaf litter are identified as a priority for future research.

Modeling the land surface heat exchange process with the aid of moderate resolution imaging spectroradiomer images

Most ecosystems and crops experience water stress in arid and semiarid areas of the Inner Mongolia grassland, Northern China. Yet the lack of long-term in situ monitoring data hinders the managerial capacity of changing water vapor environment, which is tied with sustaining the grassland in the Inner Mongolia. Environmental remote sensing monitoring and modeling may provide synergistic means of observing changes in thermodynamic balance during drought onset at the grassland surface, providing reliable projections accounting for variations and correlations of water vapor and heat fluxes. It is the aim of this paper to present a series of estimates of latent heat, sensible heat, and net radiation using an innovative first-principle, physics-based model (GEOMOD: GEO-model estimated the land surface heat with MODis data) with the aid of integrated satellite remote sensing and in situ eddy covariance data. Based on the energy balance principle and aerodynamics diffusion theory, the GEOMOD model is featured with MODIS (Moderate Resolution Imaging Spectroradiometer) data with 250 m spatial resolution to collectively reflect the spatial heterogeneity of surface properties, supplement missing data with the neighborhood values across both spatial and temporal domains, estimate the surface roughness height and zero-plane displacement with dynamic look-up table, and implement a fast iterative algorithm to calculate sensible heat. Its analytical framework is designed against overreliance on local micro-meteorological parameters. Practical implementation was assessed in the study area, the Xilin Gol River Basin, a typical grassland environment, Northern China. With 179 days of MODIS data in support of modeling, coincident ground-based observations between 2000 and 2006 were selected for model calibration. The findings indicate that GEOMOD performs reasonably well in modeling the land surface heat exchange process, as demonstrated by a case study of Inner Mongolia.

Morning Boundary-Layer Turbulent Kinetic Energy by Theoretical Models

A major factor that influences the diurnal variation of turbulent kinetic energy (TKE) is the sensible heat flux at the surface. Here, the TKE variations are analysed during the morning transition phase because subsequent to the neutral or stable stratification during the night, peaks of concentration of scalars develop. The characteristics of the TKE during the growth phase of convection are analysed with the help of two analytical models. For this purpose, a three-dimensional spectral model of the growth of convection, starting from a neutral layer, and other formulations of micrometeorological parameters such as the convective and neutral spectra, velocity variance and dissipation rates are utilised. The peak values in the TKE spectra in the lower, middle and upper levels of the convective boundary layer showed a migration to higher wavelengths as the convection increased with time. The TKE evolutions generated by the analytical models agree fairly well with the results of large-eddy simulation for three vertical levels.