Weakening of lower tropospheric temperature gradient between Indian landmass and neighbouring oceans and its impact on Indian monsoon
S M Bawiskar
Indian Institute of Tropical Meteorology, Dr. Homi Bhabha Road, Pune 411 008, India.
e-mail: bawiskar@hotmail.com bawiskar@tropmet.res.in

Abstract: The study shows that in the scenario of global warming temperature gradient (TG) between Indian landmass and Arabian Sea/Bay of Bengal is significantly decreasing in the lower troposphere with maxima around 850 hPa. TG during pre-monsoon (March to May) is reducing at a significant rate of 0.036◦/year (Arabian Sea) and 0.030◦/year (Bay of Bengal). The above alarming results are based on sixty years (1948–2007) of daily temperature and wind data extracted from CDAS-NCEP/NCAR reanalysis datasets. TG based on ERA-40 data also indicates a decreasing trend of 0.0229◦/year and 0.0397◦/year for Arabian Sea and Bay of Bengal respectively. As TG is not governed by any type of significant oscillation, there is a possibility of TG tending to zero. It is further observed that the rate of warming over the oceans is more than that over the land which has resulted into the weakening of TG. Pre-monsoon TG has significant correlations with
• All India Seasonal Monsoon Rainfall (AISMR),
• kinetic energy of waves 1 and 2 at 850 hPa,
• kinetic energy, and
• stream function at 850 hPa over Indian landmass during monsoon season.
Except AISMR, the decreasing trends observed in all the above parameters are significant. All India rainfall for July and August together shows a significant decreasing trend of 0.995mm/year. Reducing number of depressions and cyclonic storms and increasing number of break days during monsoon over India are the reflections of the weakening of TG.


Polarized microwave forward model simulations
for tropical storm Fanoos
C Balaji1,∗, M Deiveegan1, S P Venkateshan1, R M Gairola2,
A Sarkar2 and V K Agarwal2
1Department of Mechanical Engineering, Indian Institute of Technology Madras, Chennai 600 036, India.
2Meteorology and Oceanography Group, Space Applications Centre, ISRO, Ahmedabad, India.
∗e-mail: balaji@iitm.ac.in

Abstract: In the present study, forward radiative transfer simulations are carried out for the tropical cyclone Fanoos that hit the coast off south India in December 2005. The in-house radiative transfer package used for this study employs the doubling and adding method to calculate radiances leaving the top of the one dimensional precipitating atmosphere. The particle drop size distribution is assumed to follow a modified gamma distribution in respect of the cloud liquid water and cloud ice water content. For precipitation, the Marshall–Palmer particle size distribution is used. All the hydrometeor particles are assumed to be spherical and Lorentz Mie theory is used to evaluate the interaction parameters like absorption, scattering coefficients and polarized scattering matrix. In order to validate the drop size distributions and interaction parameter calculations, the simulated brightness temperatures are compared with the TMI measured brightness temperatures for all the channels. For carrying out this exercise, vertical hydrometeors retrieved by TMI are used as input. The differences between simulated and measured brightness temperatures are found to be within ±10%. The maximum difference in the brightness temperatures between the present work and the Eddington model which the TRMM algorithm employs is about 4.5K. This may become significant when retrieval of precipitation is attempted by combining the forward model with a suitable retrieval strategy, under tropical conditions.


Track prediction of very severe cyclone ‘Nargis’ using high resolution weather research forecasting (WRF) model
D R Pattanaik and Y V Rama Rao
India Meteorological Department, Lodhi Road, Mausam Bhawan, New Delhi 110 003, India.

Abstract: The recent very severe cyclonic storm (VSCS) ‘Nargis’ over the Bay of Bengal caused widespread destruction over Myanmar after hitting the coast on 2 May 2008. The real time forecasting of the VSCS ‘Nargis’ was a very difficult task as it did not follow the normal westerly/northwesterly track. In the present study, a detailed diagnostic analysis of the system ‘Nargis’ is carried out initially to investigate the features associated with this unusual movement and subsequently the real time forecast of VSCS ‘Nargis’ using high resolution advanced version weather research forecasting (WRF) model is presented. The advanced research WRF model was run for 72 h at 27 km and 20 km resolutions with 28, 29, 30 April and 1 May as the initial conditions. The diagnostic study indicates that the recurvature of the system ‘Nargis’ was mainly associated with:
• upper level southerly/southwesterly steering wind at 200 hPa level associated with anticyclonic
circulation over southeastern sector of the centre of the system,
• higher SST (29◦C or more) with higher positive anomalies over the region to the northeast of
the cyclone centre, and
• large negative 24 h pressure changes and large vorticity maximum to the east of the system.

The real time track forecast using theWRF model run at 27 km and 20 km resolution based on the initial conditions of 28 April (when the system was only 550 km away from the Indian coast) indicated that the system had a northeasterly forecast track and was not expected to cross the Indian coast. Similarly, based on 29 April initial condition the system showed east/east-northeasterly movement towards the Myanmar coast. The east/east-northeasterly movement of the ‘Nargis’ was persisting in the forecast based on 30 April and 1 May initial conditions with respective landfall errors of 85 km and 50 km with 27 km resolution, which reduces to 30 km and 40 km respectively with  20 km resolution, however, with a landfall time delay of about 10 h. Improvement of mean forecast errors at different forecast hours is noticed in WRF model run at higher resolution compared to that run at lower resolution. Thus, it is very clear that the advanced version WRF model had captured movement of the system reasonably well almost 3 days in advance. Consistence with the diagnostic analysis the WRF model forecast also indicates southerly/southwesterly strong steering wind at 200 hPa level and maximum pressure fall to the east of the system. 



Wind-driven estuarine turbidity maxima in Mandovi Estuary, central west coast of India
Pratima M Kessarkar, V Purnachandra Rao∗, R Shynu, Ishfaq Mir Ahmad,
Prakash Mehra, G S Michael and D Sundar
National Institute of Oceanography, Dona Paula 403 004, Goa, India.
∗e-mail: vprao@nio.org

Abstract: Systematic studies on the suspended particulate matter (SPM) measured on a seasonal cycle in the Mandovi Estuary, Goa indicate that the average concentrations of SPM at the regular station are ∼20mg/l, 5mg/l, 19mg/l and 5mg/l for June–September, October–January, February–April and May, respectively. SPM exhibits low-to-moderate correlation with rainfall indicating that SPM is also influenced by other processes. Transect stations reveal that the SPM at sea-end stations of the estuary are at least two orders of magnitude greater than those at the river-end during the monsoon. Estuarine turbidity maximum (ETM) of nearly similar magnitude occurs at the same location in two periods, interrupted by a period with very low SPM concentrations. The ETM occurring in June–September is associated with low salinities; its formation is attributed to the interactions between strong southwesterly winds (5.1–5.6ms−1) and wind-induced waves and tidal currents and, dominant easterly river flow at the mouth of the estuary. The ETM occurring in February–April is associated with high salinity and is conspicuous. The strong NW and SW winds (3.2–3.7ms−1) and wind-driven waves and currents seem to have acted effectively at the mouth of the estuary in developing turbidity maximum. The impact of sea breeze appears nearly same as that of trade winds and cannot be underestimated in sediment resuspension and deposition.


Comparison of two split-window methods for retrieving
land surface temperature from MODIS data
Shaohua Zhao1,2,3,∗, Qiming Qin1, Yonghui Yang2, Yujiu Xiong3 and Guoyu Qiu3
1Institute of Remote Sensing and Geographic Information System, Peking University, Beijing 100 871, China.
2Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, Chinese
Academy of Sciences, Shijiazhuang 050 021, China.
3State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Resources Science
and Technology, Beijing Normal University, Beijing 100 875, China.
∗e-mail: zshyytt@126.com

Abstract: Land surface temperature (LST) is a key parameter in environment and earth science study, especially
for monitoring drought. The objective of this work is a comparison of two split-window
methods: Mao method and Sobrino method, for retrieving LST using MODIS (Moderate-resolution
Imaging Spectroradiometer) data in North China Plain. The results show that the max, min and
mean errors of Mao method are 1.33K, 1.54K and 0.13K lower than the standard LST product
respectively; while those of Sobrino method are 0.73K, 1.46K and 1.50K higher than the standard
respectively. Validation of the two methods using LST product based on weather stations
shows a good agreement between the standard and Sobrino method, with RMSE of 1.17K, whereas
RMSE of Mao method is 1.85K. Finally, the study introduces the Sobmao method, which is based
on Sobrino method but simplifies the estimation of atmospheric water vapour content using Mao
method. The Sobmao method has almost the same accuracy with Sobrino method. With high accuracy
and simplification of water vapour content estimation, the Sobmao method is recommendable
in LST inversion for good application in Ningxia region, the northwest China, with mean error of
0.33K and the RMSE value of 0.91K.


A case study of atmospheric boundary layer features
during winter over a tropical inland station –
Kharagpur (22.32◦N, 87.32◦E)
Denny P Alappattu∗, P K Kunhikrishnan, Marina Aloysius and M Mohan
Space Physics Laboratory, Vikram Sarabhai Space Centre, Trivandrum 695 022, India.
∗e-mail: dennyalp@gmail.com

Abstract: The local weather and air quality over a region are greatly influenced by the atmospheric
boundary layer (ABL) structure and dynamics. ABL characteristics were measured using a tethered
balloon-sonde system over Kharagpur (22.32◦N, 87.32◦E, 40m above MSL), India, for the period
7 December 2004 to 30 December 2004, as a part of the Indian Space Research Organization–
Geosphere Biosphere Program (ISRO–GBP) Aerosol Land Campaign II. High-resolution data of
pressure, temperature, humidity, wind speed and wind direction were archived along with surface
layer measurements using an automatic weather station. This paper presents the features of ABL,
like ABL depth and nocturnal boundary layer (NBL) depth. The sea surface winds from Quikscat
over the oceanic regions near the experiment site were analyzed along with the NCEP/NCAR
reanalysis winds over Kharagpur to estimate the convergence of wind, moisture and vorticity to
understand the observed variations in wind speed and relative humidity, and also the increased
aerosol concentrations. The variation of ventilation coefficient (V C), a factor determining the air
pollution potential over a region, is also discussed in detail.


Deformation mechanisms in the frontal Lesser Himalayan
Duplex in Sikkim Himalaya, India
Abdul Matin1 and Sweety Mazumdar2,∗
1Department of Geology, University of Calcutta, 35 Ballygunge Circular Road, Kolkata 700 019, India.
2Department of Geology, Presidency College, Kolkata 700 073, India.
e-mail: amatinindia@yahoo.com

Abstract: Understanding deformation mechanisms in Himalayan rocks is a challenging proposition due to
the complex nature of the deformed rocks and their genesis. Crustal deformation in the Himalayan
thrust belt typically occurs in elastico-frictional (EF) or quasi-plastic (QP) regimes at depths
controlled mainly by regional strain-rate and geothermal gradient. However, material property,
grain-size and their progressive changes during deformation are also important controlling factors.
We present evidence of EF deformation from Gondwana rocks developed during the emplacement
of one of the frontal horses (Jorthang horse) in the Lesser Himalayan Duplex (LHD) structure
associated with Lesser Himalayan rocks in the footwall of the Ramgarh thrust in the Rangit window
near Jorthang in the Sikkim Himalaya. The rocks in the horse exhibit systematic changes in microand
meso-structures from an undeformed protolith to cataclasite suggesting that it was emplaced
under elastico-frictional conditions. Meso- to micro-scale shear fractures are seen developed in
Gondwana sandstone and slate while intercalated fine-grained shale-coal-carbonates are deformed
by cataclastic flow suggesting that material property and grain-size have played an important role
in the deformation of the Jorthang horse. In contrast, the hanging wall schists and quartzites of
the Ramgarh thrust exhibit quasi-plastic deformation structures. This suggests that the Jorthang
horse was emplaced under shallower crustal conditions than the antiformally folded Ramgarh thrust
sheet even though the Ramgarh sheet presently overlies the Jorthang horse.


SCS-CN and GIS-based approach for identifying
potential water harvesting sites in the Kali
Watershed, Mahi River Basin, India
D Ramakrishnan, A Bandyopadhyay and K N Kusuma
Department of Earth Sciences, Indian Institute of Technology (IIT), Powai, Mumbai 400 076, India.

Abstract: The Kali sub-watershed is situated in the semi-arid region of Gujarat, India and forms a part
of the Mahi River Watershed. This watershed receives an average annual rainfall of 900mm
mainly between July and September. Due to high runoff potential, evapo-transpiration and poor
infiltration, drought like situation prevails in this area from December to June almost every year. In
this paper, augmentation of water resource is proposed by construction of runoff harvesting structures
like check dam, percolation pond, farm pond, well and subsurface dyke. The site suitability
for different water harvesting structures is determined by considering spatially varying parameters
like runoff potential, slope, fracture pattern and micro-watershed area. GIS is utilised as a tool to
store, analyse and integrate spatial and attribute information pertaining to runoff, slope, drainage
and fracture. The runoff derived by SCS-CN method is a function of runoff potential which can be
expressed in terms of runoff coefficient (ratio between the runoff and rainfall) which can be classified
into three classes, viz., high (>40%), moderate (20–40%) and low (<20%). In addition to IMSD,
FAO specifications for water harvesting/recharging structures, parameters such as effective storage,
rock mass permeability are herein considered to augment effective storage. Using the overlay and
decision tree concepts in GIS, potential water harvesting sites are identified. The derived sites are
field investigated for suitability and implementation. In all, the accuracy of the site selection at
implementation level varies from 80–100%.


Laboratory technique for quantitative thermal emissivity
measurements of geological samples
George Mathew1,∗, Archana Nair1, T K Gundu Rao2 and Kanchan Pande1
1Department of Earth Sciences, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India.
2Sophisticated Analytical Instrumentation Centre, Indian Institute of Technology, Bombay,
Powai, Mumbai 400 076, India.
∗e-mail: gmathew@iitb.ac.in

Abstract: Thermal infrared spectroscopy is a powerful technique for the compositional analysis of geological
materials. The spectral feature in the mid-IR region is diagnostic of the mineralogy and spectral
signatures of mixtures of minerals that add linearly, and therefore, can be used as an important
tool to determine the mineralogy of rocks in the laboratory and remotely for planetary exploration.
The greatest challenge in the emission measurement lies in the measurement of the weak thermal
photons emitted from geological materials in a laboratory setup, and accurately records the
temperature of the rock sample. The present work pertains to the details of a new Thermal Emission
Spectrometer (TES) laboratory that has been developed under the ISRO Planetary Science
and Exploration (PLANEX) programme, for emission related mineralogical investigations of planetary
surfaces. The focus of the paper is on the acquisition and calibration technique for obtaining
emissivity, and the deconvolution procedure to obtain the modal abundances of the thermal emission
spectra in the range of 6–25 μm using Fourier Transform Infrared (FTIR) spectroscopy. The
basic technique is adopted from the work of Ruff et al (1997). This laboratory at the Department
of Earth Sciences, IIT-Bombay is currently developing pure end mineral library of mineral particulates
(<65 μm), and adding new end members to the existing ASU spectral library. The paper
argues the need for considering Lunar Orbiter Thermal Emission Spectrometer (LOTES) for future
Indian Moon mission programme (Chandrayan-II) to determine evidences of varied lithologies on
the lunar surface.



Mesoscale model simulation of low level equatorial winds
over Borneo during the haze episode of September 1997
Mastura Mahmud
Earth Observation Centre, Faculty of Social Sciences and Humanities,
Universiti Kebangsaan Malaysia, Bangi 43600, Selangor, Malaysia.
e-mail: mastura@pkrisc.cc.ukm.my

Abstract: The large-scale vegetation fires instigated by the local farmers during the dry period of the
major El Ni˜no event in 1997 can be considered as one of the worst environmental disasters that
have occurred in southeast Asia in recent history. This study investigated the local meteorology
characteristics of an equatorial environment within a domain that includes the northwestern
part of Borneo from the 17 to 27 September 1997 during the height of the haze episode by
utilizing a limited area three-dimensional meteorological and dispersion model, The Air Pollution
Model (TAPM).
Daily land and sea breeze conditions near the northwestern coast of Borneo in the state of
Sarawak, Malaysia were predicted with moderate success by the index of agreement of less than
one between the observed and simulated values for wind speed and a slight overprediction of 2.3
of the skill indicator that evaluates the standard deviation to the observed values. The innermost
domain of study comprises an area of 24,193 km2, from approximately 109◦E to 111◦E, and
from 1◦N to 2.3◦N, which includes a part of the South China Sea. Tracer analysis of air particles
that were sourced in the state of Sarawak on the island of Borneo verified the existence of the
landward and shoreward movements of the air during the simulation of the low level wind field.
Polluted air particles were transported seawards during night-time, and landwards during daytime,
highlighting the recirculation features of aged and newer air particles during the length of eleven
days throughout the model simulation. Near calm conditions at low levels were simulated by the
trajectory analysis from midnight to mid-day on the 22 of September 1997. Low-level turbulence
within the planetary boundary layer in terms of the total kinetic energy was weak, congruent
with the weak strength of low level winds that reduced the ability of the air to transport the
pollutants.
Statistical evaluation showed that parameters such as the systematic RMSE and unsystematic
RMSE between the observed and simulated values indicated the modest skill of the model
in simulating the low level winds. Otherwise, the equatorial meteorological parameters such as
wind speed and temperature were successfully simulated by the model with comparatively high
correlation coefficients, lower RMSEs and moderately high indices of agreement with observed
values.



Magnetic anomalies of offshore Krishna–Godavari basin,
eastern continental margin of India
K V Swamy1, I V Radhakrishna Murthy2, K S Krishna3,∗, K S R Murthy4,
A S Subrahmanyam4 and M M Malleswara Rao4
1Department of Geo-informatics, Adikavi Nannaya University, Rajahmundry 533 105, India.
2Department of Geophysics, Andhra University, Visakhapatnam 530 003, India.
3National Institute of Oceanography, Council of Scientific and Industrial Research,
Dona Paula, Goa 403 004, India.
4Regional Centre, National Institute of Oceanography, Council of Scientific and
Industrial Research, Visakhapantam 530 017, India.
∗e-mail: krishna@nio.org

Abstract: The marine magnetic data acquired from offshore Krishna–Godavari (K–G) basin, eastern continental
margin of India (ECMI), brought out a prominent NE–SW trending feature, which could
be explained by a buried structural high formed by volcanic activity. The magnetic anomaly feature
is also associated with a distinct negative gravity anomaly similar to the one associated with
85◦E Ridge. The gravity low could be attributed to a flexure at the Moho boundary, which could
in turn be filled with the volcanic material. Inversion of the magnetic and gravity anomalies was
also carried out to establish the similarity of anomalies of the two geological features (structural
high on the margin and the 85◦E Ridge) and their interpretations. In both cases, the magnetic
anomalies were caused dominantly by the magnetization contrast between the volcanic material
and the surrounding oceanic crust, whereas the low gravity anomalies are by the flexures of the
order of 3–4 km at Moho boundary beneath them. The analysis suggests that both structural high
present in offshore Krishna–Godavari basin and the 85◦E Ridge have been emplaced on relatively
older oceanic crust by a common volcanic process, but at discrete times, and that several of the
gravity lows in the Bay of Bengal can be attributed to flexures on the Moho, each created due to
the load of volcanic material.