scholarly journals Seasonal prediction of cyclonic disturbances over the Bay of Bengal during summer monsoon season : Identification of potential predictors

MAUSAM ◽  
2021 ◽  
Vol 61 (4) ◽  
pp. 469-486
Author(s):  
M. MOHAPATRA ◽  
S. ADHIKARY
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Large Scale ◽  
Monsoon Season ◽  
Equatorial Indian Ocean ◽  
Seasonal Prediction ◽  
Reanalysis Data ◽  
Scale Field ◽  
Large Scale Field ◽  
Cyclonic Disturbances

The cyclonic disturbances (CD) over the Bay of Bengal during monsoon season have significant impact on rainfall over India. On many occasions, they cause flood leading to loss of lives and properties. Hence, any early information about the frequency of occurrence of such disturbances will help immensely the disaster managers and planners. However, the studies are limited on the seasonal prediction of CD over the Bay of Bengal unlike other Ocean basins of the world. Hence, a study has been undertaken to find out the potential predictors during the months of April and May for prediction of frequency of cyclonic disturbances over the Bay of Bengal during monsoon season (June – September). For this purpose, best track data of India Meteorological Department and large scale field parameters based on NCEP/NCAR reanalysis data have been analyzed for the period of 1948 – 2007.  The linear correlation analysis has been applied between frequency of CD and large scale field parameters based on NCEP/NCAR reanalysis data to find out the potential predictors.   The large scale field parameters over the equatorial Indian Ocean, especially over west equatorial Indian Ocean and adjoining Arabian Sea (up to 15° N) should be favourable in April and May with lower mean sea level pressure (MSLP), lower geopotential heights and stronger southerlies in lower and middle levels, along with stronger northerly components at upper level for higher frequency of CD during subsequent monsoon season. Consequently, there should be increase in relative humidity (RH) and precipitable water content and decrease in outgoing longwave radiation (OLR) and temperature at lower levels over this region during April and May for higher frequency of CD during subsequent monsoon  season. Comparing the area of significant correlation between frequency of CD and large scale field parameters and its stability from April to September, MSLP and geopotential heights are most influencing parameters followed by OLR, sea surface temperature, air temperature and RH at 850 hPa level.

scholarly journals Cloud climatology of the Indian Ocean based on ship observations

MAUSAM ◽  
2022 ◽  
Vol 52 (3) ◽  
pp. 527-540
Author(s):  
M. RAJEEVAN ◽  
R. K. PRASAD ◽  
U. S. DE
Keyword(s):  
Indian Ocean ◽  
Bay Of Bengal ◽  
Cloud Cover ◽  
Monsoon Season ◽  
Equatorial Indian Ocean ◽  
Enso Events ◽  
Decadal Scale ◽  
Low Cloud ◽  
The Indian Ocean ◽  
Low Cloud Cover

Surface cloud data based on synoptic observations made by Voluntary Observing Ships (VOS) during the period 1951-98 were used to prepare the seasonal and annual cloud climatology of the Indian Ocean. The analysis has been carried out by separating the long-term trends, decadal and inter-annual components from the monthly cloud anomaly time series at each 5° × 5° grids.   Maximum zone of total and low cloud cover shifts from equator to northern parts of India during the monsoon season. During the monsoon season (June-September), maximum total cloud cover exceeding 70% and low cloud cover exceeding 50% are observed over north Bay of Bengal. Maximum standard deviation of total and low cloud cover is observed near the equator and in the southern hemisphere. Both total and low cloud cover over Arabian Sea and the equatorial Indian Ocean are observed to decrease during the ENSO events. However, cloud cover over Bay of Bengal is not modulated by the ENSO events. On inter-decadal scale, low cloud cover shifted from a "low regime" to a "high regime" after 1980 which may be associated with the corresponding inter-decadal changes of sea surface temperatures over north Indian Ocean observed during the late 1970s.

Characteristics of 3–4- and 6–8-Day Period Disturbances Observed over the Tropical Indian Ocean

2010 ◽  
Vol 138 (11) ◽  
pp. 4158-4174 ◽  
Author(s):  
Kazuaki Yasunaga ◽  
Kunio Yoneyama ◽  
Qoosaku Moteki ◽  
Mikiko Fujita ◽  
Yukari N. Takayabu ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Rossby Waves ◽  
Equatorial Indian Ocean ◽  
Tropical Indian Ocean ◽  
Meridional Wind ◽  
Reanalysis Data ◽  
Japan Meteorological Agency ◽  
Climate Data ◽  
Convectively Coupled Waves

Abstract A field observational campaign [i.e., the Mirai Indian Ocean cruise for the Study of the MJO-convection Onset (MISMO)] was conducted over the central equatorial Indian Ocean in October–December 2006. During MISMO, large-scale organized convection associated with a weak Madden–Julian oscillation (MJO) broke out, and some other notable variations were observed. Water vapor and precipitation data show a prominent 3–4-day-period cycle associated with meridional wind υ variations. Filtered υ anomalies at midlevels in reanalysis data [i.e., the Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS)] show westward phase velocities, and the structure is consistent with mixed Rossby–gravity waves. Estimated equivalent depths are a few tens of meters, typical of convectively coupled waves. In the more rainy part of MISMO (16–26 November), the 3–4-day waves were coherent through the lower and midtroposphere, while in the less active early November period midlevel υ fluctuations appear less connected to those at the surface. SST diurnal variations were enhanced in light-wind and clear conditions. These coincided with westerly anomalies in prominent 6–8-day zonal wind variations with a deep nearly barotropic structure through the troposphere. Westward propagation and structure of time-filtered winds suggest n = 1 equatorial Rossby waves, but with estimated equivalent depth greater than is common for convectively coupled waves, although sheared background flow complicates the estimation somewhat. An ensemble reanalysis [i.e., the AGCM for the Earth Simulator (AFES) Local Ensemble Transform Kalman Filter (LETKF) Experimental Reanalysis (ALERA)] shows enhanced spread among the ensemble members in the zonal confluence phase of these deep Rossby waves, suggesting that assimilating them excites rapidly growing differences among ensemble members.

scholarly journals An analysis of monthly rainfall and the meteorological conditions associated with the deficient rainfall towards the end of 2017 southwest monsoon season

MAUSAM ◽  
2021 ◽  
Vol 71 (3) ◽  
pp. 391-404
Author(s):  
ARTI BANDGAR ◽  
PRABHU PALLAVI ◽  
SREEJITH O P ◽  
PAI D S
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Monsoon Season ◽  
Equatorial Indian Ocean ◽  
Longwave Radiation ◽  
Southwest Monsoon ◽  
Sst Forcing ◽  
The Indian Ocean ◽  
Neutral Conditions ◽  
Southwest Monsoon Season

This paper studies the summer monsoon 2017 and examines the number of parameters which we believe were important in understanding why monsoon failed in second half over India. The list of parameters includes monthly mean or anomalies of the following fields : sea surface temperature, outgoing longwave radiation, stream function of lower and upper atmosphere, velocity potential and monthly and seasonal precipitation. ENSO conditions were mainly neutral with warm ENSO neutral conditions observed in the first half and cool ENSO neutral conditions observed in the second half. As a result, influence on the monsoon from the large scale SST forcing from Pacific Ocean was nearly absent during the season. However, Positive IOD conditions over the Indian Ocean during the monsoon season, particularly during first half of the monsoon were prominent. The transition of warmer than normal SSTs (June and July) to normal SSTs (August) and then becoming cooler than normal SSTs (September) in the equatorial Indian Ocean had a significant influence which lead monsoon to fail in second half.   

Observations of Upper-Tropospheric Temperature Inversions in the Indian Monsoon and Their Links to Convectively Forced Quasi-Stationary Kelvin Waves

2020 ◽  
Vol 77 (8) ◽  
pp. 2835-2846 ◽  
Author(s):  
Richard Newton ◽  
William Randel
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Indian Monsoon ◽  
Monsoon Season ◽  
Deep Convection ◽  
Equatorial Indian Ocean ◽  
Kelvin Waves ◽  
Tropospheric Temperature ◽  
Time Behavior ◽  
Temperature Inversions

Abstract High-vertical-resolution temperature measurements from GPS radio occultation data show frequent upper-tropospheric inversions over the equatorial Indian Ocean during the summer monsoon season. Each year, around 30% of profiles in this region have temperature inversions near 15 km during the monsoon season, peaking during July–September. This work describes the space–time behavior of these inversions, and their links to transient deep convection. The Indian Ocean inversions occur episodically several times each summer, with a time scale of 1–2 weeks, and are quasi stationary or slowly eastward moving. Strong inversions are characterized by cold anomalies in the upper-troposphere (12–15 km), warm anomalies in the tropopause layer (16–18 km), and strong zonal wind anomalies that are coherent with temperature anomalies. Temperature and wind anomalies are centered over the equator and show a characteristic eastward phase tilt with height with a vertical wavelength near 5 km, consistent with a Kelvin wave structure. Composites of outgoing longwave radiation (OLR) show that strong inversions are linked to enhanced deep convection over the equatorial Indian Ocean, preceding the inversions by ~2–6 days. These characteristics suggest that the inversions are linked to convectively forced Kelvin waves, which are Doppler shifted by the easterly monsoonal winds such that they remain quasi stationary in the equatorial Indian Ocean. These large-scale waves influence circulation on the equatorial side of the Indian monsoon anticyclone; they may provide a positive feedback to the underlying convection, and are possibly linked with regions of shear-induced turbulence.

Biodata response elaboration: A large-scale field experiment

2010 ◽  
Author(s):  
Julia Levashina ◽  
Frederick P. Morgeson ◽  
Michael A. Campion
Keyword(s):  
Field Experiment ◽  
Large Scale ◽  
Scale Field ◽  
Large Scale Field

Hybrid Combination of GIS,GPS,WSN and GPRS Technology in Modern Digital Agriculture Application

2010 ◽  
Vol 108-111 ◽  
pp. 1158-1163 ◽  
Author(s):  
Peng Cheng Nie ◽  
Di Wu ◽  
Weiong Zhang ◽  
Yan Yang ◽  
Yong He
Keyword(s):  
Large Scale ◽  
Field Application ◽  
Wireless Sensor ◽  
Information Collection ◽  
Scale Field ◽  
Large Scale Field ◽  
Field Information ◽  
Intelligent Management ◽  
Digital Agriculture ◽  
And Control

In order to improve the information management of the modern digital agriculture, combined several modern digital agriculture technologies, namely wireless sensor network (WSN), global positioning system (GPS), geographic information system (GIS) and general packet radio service (GPRS), and applied them to the information collection and intelligent control process of the modern digital agriculture. Combining the advantage of the local multi-channel information collection and the low-power wireless transmission of WSN, the stable and low cost long-distance communication and data transmission ability of GPRS, the high-precision positioning technology of the DGPS positioning and the large-scale field information layer-management technology of GIS, such a hybrid technology combination is applied to the large-scale field information and intelligent management. In this study, wireless sensor network routing nodes are disposed in the sub-area of field. These nodes have GPS receiver modules and the electric control mechanism, and are relative positioned by GPS. They can real-time monitor the field information and control the equipment for the field application. When the GPS position information and other collected field information are measured, the information can be remotely transmitted to PC by GPRS. Then PC can upload the information to the GIS management software. All the field information can be classified into different layers in GIS and shown on the GIS map based on their GPS position. Moreover, we have developed remote control software based on GIS. It can send the control commands through GPRS to the nodes which have control modules; and then we can real-time manage and control the field application. In conclusion, the unattended automatic wireless intelligent technology for the field information collection and control can effectively utilize hardware resources, improve the field information intelligent management and reduce the information and intelligent cost.

scholarly journals Tropical Cyclone Count Forecasting Using a Dynamical Seasonal Prediction System: Sensitivity to Improved Ocean Initialization

2011 ◽  
Vol 24 (12) ◽  
pp. 2963-2982 ◽  
Author(s):  
Andrea Alessandri ◽  
Andrea Borrelli ◽  
Silvio Gualdi ◽  
Enrico Scoccimarro ◽  
Simona Masina
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Wind Shear ◽  
Large Scale ◽  
Initial Conditions ◽  
North Pacific Ocean ◽  
Convective Available Potential Energy ◽  
Seasonal Prediction ◽  
Boreal Summer ◽  
Prediction System

Abstract This study investigates the predictability of tropical cyclone (TC) seasonal count anomalies using the Centro Euro-Mediterraneo per i Cambiamenti Climatici–Istituto Nazionale di Geofisica e Vulcanologia (CMCC-INGV) Seasonal Prediction System (SPS). To this aim, nine-member ensemble forecasts for the period 1992–2001 for two starting dates per year were performed. The skill in reproducing the observed TC counts has been evaluated after the application of a TC location and tracking detection method to the retrospective forecasts. The SPS displays good skill in predicting the observed TC count anomalies, particularly over the tropical Pacific and Atlantic Oceans. The simulated TC activity exhibits realistic geographical distribution and interannual variability, thus indicating that the model is able to reproduce the major basic mechanisms that link the TCs’ occurrence with the large-scale circulation. TC count anomalies prediction has been found to be sensitive to the subsurface assimilation in the ocean for initialization. Comparing the results with control simulations performed without assimilated initial conditions, the results indicate that the assimilation significantly improves the prediction of the TC count anomalies over the eastern North Pacific Ocean (ENP) and northern Indian Ocean (NI) during boreal summer. During the austral counterpart, significant progresses over the area surrounding Australia (AUS) and in terms of the probabilistic quality of the predictions also over the southern Indian Ocean (SI) were evidenced. The analysis shows that the improvement in the prediction of anomalous TC counts follows the enhancement in forecasting daily anomalies in sea surface temperature due to subsurface ocean initialization. Furthermore, the skill changes appear to be in part related to forecast differences in convective available potential energy (CAPE) over the ENP and the North Atlantic Ocean (ATL), in wind shear over the NI, and in both CAPE and wind shear over the SI.

Sign in / Sign up

Export Citation Format

Share Document