M.N. Patil

An Overview of the Land Surface Processes Experiment (Laspex) over a Semi-Arid Region of India

To understand and quantify the land-surface-vegetation interactionwith the atmospheric boundary layer, and validate or improve upon the existing surfaceflux parameterization schemes in various weather forecast models, a LAnd SurfaceProcesses EXperiment (LASPEX), was designed and executed in the semi-arid regionof Gujarat, India during January 1997–December 1998. Micrometeorological tower observations,soil and vegetation parameters, radiation, turbulence and upper airobservations were taken continuously for two years at five sites, separated by about60–100 km from each other. Towers of 9 m height with instruments at four levels wereinstalled at sites that are agricultural fields and characterized with a variety of soilproperties, vegetation and diverse crops. An overview of the experiment is presented.Some results, such as the seasonal variation of surface energy balance and turbulence statistics,are discussed.

Relationship Between the Momentum and Scalar Fluxes Close to the Ground During the Indian Post-monsoon Period

Results of a comprehensive study of the characteristics of turbulent transport very close to the ground using micrometeorological eddy-covariance measurements from the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) Integrated Ground Observational Campaign (IGOC) conducted in 2011 at a rural site over the Indian peninsular region are presented. The dataset used in the present study pertains to the morning hours when the convective boundary layer is at its growing phase. A new method, very similar to the traditional quadrant analysis, is introduced to investigate the relationship between the scalar and momentum flux transports by projecting the scalar and momentum flux contours onto the

Evaluation of Noah-LSM for soil hydrology parameters in the Indian summer monsoon conditions

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The influence of wind speed on surface layer stability and turbulent fluxes over southern Indian peninsula station

u-w plane. Cospectral analysis is employed to study the scales of the transporting eddies; it was found that, during very unstable conditions, the scalar and momentum transports are poorly correlated with each other. However, for the near-neutral case, the correlation between the scalar and momentum transports becomes stronger, thus supporting the Reynolds analogy.

A study of turbulent characteristics of atmospheric boundary layer over monsoon trough region using Kytoon and Doppler sodar

Time variation of surface fluxes of heat, moisture and momentum over a sea station (20°N 89°E) in the north Bay of Bengal has been computed by profile method for the period 18th–25th August 1990 using meteorological data of MONTBLEX-90 from ORVSagarkanya. The fluxes showed synoptic and diurnal variations which are marked during depression (20th–21st August) compared to their variation prior to and after this period. Variations of heat and water vapour fluxes were in phase. Night time fluxes are relatively high compared to day time. Average momentum transfer during depression was two to three times large. Variations in Bowen ratio were relatively large during day time. During depression, it varied between 0·2 in day time and about 0·3 at night and in the undisturbed period between −0·1 and 0·2 during day time and 0·2 and 0·25 at night. The study shows that the assumptionCD=CH=CE of the exchange coefficients normally used in estimating the fluxes by the bulk aerodynamic method is not appropriate becauseCH/CD≈2,CE/CD≈1·5 andCH/CE≈1·4.

Aerodynamic drag coefficient and roughness length for three seasons over a tropical western Indian station

The micrometeorological observations, collected over a station in Ranchi (23°45′N, 85°30′E) which is under the monsoon trough region of India, were used in the Noah-LSM (NCEP, OSU, Air Force and Office of Hydrology Land Surface Model) to investigate the model performance in wet (2009 and 2011) and dry (2010) conditions during the south-west summer monsoon season. With this analysis, it is seen that the Noah-LSM has simulated the diurnal cycle of heat fluxes (sensible and ground) reasonably. The simulated heat fluxes were compared with its direct measurements by sonic anemometer and soil heat flux plate. The net radiation and sensible heat flux are simulated well by the model, but the simulation of ground heat flux was found to be poor in both dry as well as wet conditions. The soil temperature simulations were also found to be poor in 0–5- and 5–10-cm layers compared to other deeper layers. The observations were also correlated with the Modern Era Retrospective-analysis for Research and Applications (MERRA) data. The correlation between the observations and ground heat flux was better in MERRA dataset than that of the Noah-LSM simulation.

Lightning and middle atmospheric discharges in the atmosphere

Abstract Land Surface Processes Experiment was conducted in the year 1997 in which land surface observations were collected over a tropical semi-arid region of Gujarat, India. Using these observations, Noah Land Surface Model version 2.7.1 (Noah-LSM) has been tested in the wet and dry surface conditions for four test sites, viz., Anand (22°35′ N, 72°55′ E), Derol (22°40′ N, 73°45′ E), Arnej (22°40′ N, 72°15′ E), and Khandha (22°02′ N, 73°11′ E) having different soil texture (sandy loam and clay). Model simulations for net radiation, skin temperature, and soil temperature at various depths were compared with observations. Initial results of soil and surface temperature showed good agreement for clay soil texture compared with sandy loam textures during dry periods. In contrast, for wet periods. Contrastingly, for wet periods, the net radiation and skin temperature showed better agreement for sandy loam textures than for clay textured soils. The model simulation was repeated for the sandy loam soil texture soil during dry period and for the clay texture soil during the wet period by replacing the model estimated soil thermal conductivity by the annual mean soil thermal conductivity of test stations. The results were improved for sandy loam texture but remain unchanged for clay texture. Comparison of simulated and observed parameters shows good correlation, high index of agreement, and low error. Overall, the results simulated by Noah-LSM for both soil textures are comparable with the observations.

Lightning and convective rain over Indian peninsula and Indo-China peninsula

Surface to atmosphere exchange has received much attention in numerical weather prediction models. This exchange is defined by turbulent parameters such as frictional velocity, drag coefficient and heat fluxes, which have to be derived experimentally from high-frequency observations. High-frequency measurements of wind speed, air temperature and water vapour mixing ratio (eddy covariance measurements), were made during the Integrated Ground Observation Campaign (IGOC) of Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) at Mahabubnagar, India (16∘44′N, 77∘59′E) in the south-west monsoon season. Using these observations, an attempt was made to investigate the behaviour of the turbulent parameters, mentioned above, with respect to wind speed. We found that the surface layer stability derived from the Monin–Obukhov length scale, is well depicted by the magnitude of wind speed, i.e., the atmospheric boundary layer was under unstable regime for wind speeds >4 m s−1; under stable regime for wind speeds <2 m s−1 and under neutral regime for wind speeds in the range of 2–3 m s−1. All the three stability regimes were mixed for wind speeds 3–4 m s−1. The drag coefficient shows scatter variation with wind speed in stable as well as unstable conditions.