scholarly journals Evaluation of heavy rainfall warning over India during summer monsoon season

MAUSAM ◽  
2021 ◽  
Vol 60 (4) ◽  
pp. 475-490
Author(s):  
M. MOHAPATRA ◽  
H. R. HATWAR ◽  
B. K. BANDYOPADHYAY ◽  
V. SUBRAHMANYAM
Keyword(s):  
Summer Monsoon ◽  
Heavy Rainfall ◽  
Monsoon Season ◽  
Weather Prediction ◽  
India Meteorological Department ◽  
Skill Score ◽  
Spatial And Temporal Variability ◽  
Summer Monsoon Season ◽  
Skill Scores ◽  
Heidke Skill Score

India Meteorological Department (IMD) issues heavy rainfall warning for a meteorological sub-division when the expected 24 hours rainfall over any rain gauge station in that sub-division is likely to be 64.5 mm or more. Though these warnings have been provided since the inception of IMD, a few attempts have been made for quantitative evaluation of these warnings.  Hence, a study is undertaken to verify the heavy rainfall warnings over 36 meteorological sub-divisions of India during monsoon months (June-September) and season as a whole. For this purpose, data of recent 5 years (2002-2006) has been taken into consideration. In this connection, the day when heavy rainfall is recorded over at least one station in a sub-division, has been considered as a heavy rainfall day for that sub-division.   There is a large spatial and temporal variability in skill scores of heavy rainfall warnings over India during summer monsoon season. Considering the monsoon season as a whole, the Heidke Skill Score (HSS) is relatively less (<0.20) over the regions with less frequent heavy rainfall like Lakshadweep, southeast peninsula, Vidarbha, Marathwada, Jammu & Kashmir, Arunachal Pradesh and Nagaland, Manipur, Mizoram & Tripura (NMMT). It is higher (> 0.50) over Konkan & Goa, Madhya Maharashtra and Gujarat region. There has been improvement in the forecast skill with gradual increase in the critical success index and Heidke skill score over the years mainly due to the Numerical Weather Prediction (NWP) models' guidance available to the forecasters. However, the false alarm rate and missing rate are still very high (> 0.50), especially over many sub-divisions of northwest India, southeast peninsula and NMMT.

scholarly journals Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: Ship-borne measurements and model simulations

2016 ◽  
Author(s):  
Imran A. Girach ◽  
Narendra Ojha ◽  
Prabha R. Nair ◽  
Andrea Pozzer ◽  
Yogesh K. Tiwari ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Surface Ozone ◽  
Ozone Production ◽  
Spatial And Temporal Variability ◽  
Summer Monsoon Season ◽  
Rainfall Events ◽  
Model Simulations ◽  
Mixing Ratios

Abstract. We present ship-borne measurements of surface ozone, carbon monoxide and methane over the Bay of Bengal (BoB), the first time such measurements have been taken during the summer monsoon season, as a part of the Continental Tropical Convergence Zone (CTCZ) experiment during 2009. O3, CO, and CH4 mixing ratios exhibited significant spatial and temporal variability in the ranges of 8–54 nmol mol−1, 50–200 nmol mol−1, and 1.57–2.15 µmol mol−1, with means of 29.7 ± 6.8 nmol mol−1, 96 ± 25 nmol mol−1, and 1.83 ± 0.14 µmol mol−1, respectively. The average mixing ratios of trace gases over northern BoB (O3: 30 ± 7 nmol mol−1, CO: 95 ± 25 nmol mol−1, CH4: 1.86 ± 0.12 µmol mol−1), in airmasses from northern or central India, did not differ much from those over central BoB (O3: 27 ± 5 nmol mol−1, CO: 101 ± 27 nmol mol−1, CH4: 1.72 ± 0.14 µmol mol−1), in airmasses from southern India. Spatial variability is observed to be most significant for CH4. The ship-based observations, in conjunction with backward air trajectories and ground-based measurements over the Indian region, are analyzed to estimate a net ozone production of 1.5–4 nmol mol−1 day−1 in the outflow. Ozone mixing ratios over the BoB showed large reductions (by ~ 20 nmol mol−1) during four rainfall events. Temporal changes in the meteorological parameters, in conjunction with ozone vertical profiles, indicate that these low ozone events are associated with downdrafts of free-tropospheric ozone-poor airmasses. While the observed variations in O3 and CO are successfully reproduced using the Weather Research and Forecasting model with Chemistry (WRF-Chem), this model overestimates mean concentrations by about 20 %, generally overestimating O3 mixing ratios during the rainfall events. Analysis of the chemical tendencies from model simulations for a low-O3 event on August 10, 2009, captured successfully by the model, shows the key role of horizontal advection in rapidly transporting ozone-rich airmasses across the BoB. Our study fills a gap in the availability of trace gas measurements over the BoB, and when combined with data from previous campaigns, reveals large seasonal amplitude (~ 39 and ~ 207 nmol mol−1 for O3 and CO, respectively) over the northern BoB.

scholarly journals Verification of real-time WRF-ARW forecast in IMD during monsoon 2010

MAUSAM ◽  
2021 ◽  
Vol 67 (2) ◽  
pp. 333-356
Author(s):  
ANANDA K. DAS ◽  
P. K. KUNDU ◽  
S. K. ROY BHOWMIK ◽  
M. RATHEE
Keyword(s):  
Real Time ◽  
Meteorological Parameters ◽  
Mesoscale Model ◽  
Monsoon Season ◽  
Weather Prediction ◽  
India Meteorological Department ◽  
Forecast Errors ◽  
Orographic Rainfall ◽  
Skill Scores ◽  
Model Efficiency

Performance of the mesoscale model WRF-ARW has been evaluated for whole monsoon season of 2011. The real-time model forecasts are generated day to day in India meteorological Department for short-range weather prediction over the Indian region. Verification of rainfall forecasts has been carried out against observed rainfall analysis whereas for all other meteorological parameters verification analysis which was generated using WRFDA assimilation system. Traditional continuous scores and categorical skill scores are computed over seven different zones in India in the verification of rainfall. For other parameters (upper-air as well as surface), continuous scores are evaluated with temporal and spatial features during whole season. The forecast errors of meteorological parameters other than rainfall are analyzed to portray the model efficiency in maintaining monsoon features in large scale along with localized pattern. In the study, time series of errors throughout the season also has been maneuvered to evaluate model forecasts during diverse phases of monsoon. Categorical scores suggest the model forecasts are reliable up to moderate rainfall category for all seven zones.  But, rainfall areas with rainfall above 35.5 mm per day associated with migrated weather system from Indian seas could not be predicted as the model displaces them in the forecast. The verification for a whole monsoon season has shown that the model has capability to predict orographic rainfall for the interactive areas with low level monsoon flow over Western Ghats.  The model efficiency are in general brought out for a single monsoon season and errors characteristics are discussed for further improvement which could not perceived during real-time use of the model. 

scholarly journals Simulation of Heavy Rainfall Events during Retreat Phase of Summer Monsoon Season over Parts of Andhra Pradesh

2012 ◽  
Vol 03 (04) ◽  
pp. 737-748 ◽  
Author(s):  
O. S. R. U. Bhanu Kumar ◽  
P. Suneetha ◽  
S. Ramalingeswara Rao ◽  
M. Satya Kumar
Keyword(s):  
Summer Monsoon ◽  
Andhra Pradesh ◽  
Heavy Rainfall ◽  
Monsoon Season ◽  
Summer Monsoon Season ◽  
Rainfall Events ◽  
Heavy Rainfall Events

scholarly journals Variations in O<sub>3</sub>, CO, and CH<sub>4</sub> over the Bay of Bengal during the summer monsoon season: shipborne measurements and model simulations

2017 ◽  
Vol 17 (1) ◽  
pp. 257-275 ◽  
Author(s):  
Imran A. Girach ◽  
Narendra Ojha ◽  
Prabha R. Nair ◽  
Andrea Pozzer ◽  
Yogesh K. Tiwari ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Bay Of Bengal ◽  
Monsoon Season ◽  
Spatial And Temporal Variability ◽  
Summer Monsoon Season ◽  
Rainfall Events ◽  
Air Masses ◽  
Model Simulations ◽  
Mixing Ratios ◽  
Northern India

Abstract. We present shipborne measurements of surface ozone (O3), carbon monoxide (CO), and methane (CH4) over the Bay of Bengal (BoB), the first time such measurements have been performed during the summer monsoon season, as a part of the Continental Tropical Convergence Zone (CTCZ) experiment during 2009. O3, CO, and CH4 mixing ratios exhibited significant spatial and temporal variability in the ranges of 8–54 nmol mol−1, 50–200 nmol mol−1, and 1.57–2.15 µmol mol−1, with means of 29.7 ± 6.8 nmol mol−1, 96 ± 25 nmol mol−1, and 1.83 ± 0.14 µmol mol−1, respectively. The average mixing ratios of trace gases over BoB in air masses from central/northern India (O3: 30 ± 7 nmol mol−1; CO: 95 ± 25 nmol mol−1; CH4: 1.86 ± 0.12 µmol mol−1) were not statistically different from those in air masses from southern India (O3: 27 ± 5 nmol mol−1; CO: 101 ± 27 nmol mol−1; CH4: 1.72 ± 0.14 µmol mol−1). Spatial variability is observed to be most significant for CH4 with higher mixing ratios in the air masses from central/northern India, where higher CH4 levels are seen in the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY) data. O3 mixing ratios over the BoB showed large reductions (by  ∼  20 nmol mol−1) during four rainfall events. Temporal changes in the meteorological parameters, in conjunction with O3 vertical profile, indicate that these low-O3 events are associated with downdrafts of free-tropospheric O3-poor air masses. While the observed variations of O3 and CO are successfully reproduced using the Weather Research and Forecasting model with Chemistry (WRF-Chem), this model overestimates mean concentrations by about 6 and 16 % for O3 and CO, respectively, generally overestimating O3 mixing ratios during the rainfall events. An analysis of modelled O3 along air mass trajectories show mean en route O3 production rate of about 4.6 nmol mol−1 day−1 in the outflow towards the BoB. Analysis of the various tendencies from model simulations during an event on 10 August 2009, reproduced by the model, shows horizontal advection rapidly transporting O3-rich air masses from near the coast across the BoB. This study fills a gap in the availability of trace gas measurements over the BoB and, when combined with data from previous campaigns, reveals large seasonal amplitude ( ∼  39 and  ∼  207 nmol mol−1 for O3 and CO, respectively) over the northern BoB.

Precipitation modes over the Western Ghats orography during the summer monsoon season

2021 ◽  
Author(s):  
Jayesh Phadtare ◽  
Jennifer Fletcher ◽  
Andrew Ross ◽  
Andy Turner ◽  
Thorwald Stein ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
West Coast ◽  
Western Ghats ◽  
Monsoon Season ◽  
Radiosonde Data ◽  
Summer Monsoon Season ◽  
The West ◽  
Radiosonde Station ◽  
Westerly Flow ◽  
The Western Ghats

&lt;p&gt;Precipitation distribution around an orographic barrier is controlled by the Froude Number (Fr) of the impinging flow. Fr is essentially a ratio of kinetic energy and stratification of winds around the orography. For Fr &gt; 1 (Fr &lt;1), the flow is unblocked (blocked) and precipitation occurs over the mountain peaks and the lee region (upwind region). While idealized modelling studies have robustly established this relationship, its widespread real-world application is hampered by the dearth of relevant observations. Nevertheless, the data collected in the field campaigns give us an opportunity to explore this relationship and provide a testbed for numerical models. A realistic distribution of precipitation over a mountainous region in these models is necessary for flash-flood and landslide forecasting. The Western Ghats region is a classic example where the orographically induced precipitation leads to floods and landslides during the summer monsoon season. In the recent INCOMPASS field campaign, it was shown that the precipitation over the west coast of India occurred in alternate offshore and onshore phases. The Western Ghats received precipitation predominantly during the onshore phase which was characterized by a stronger westerly flow. Here, using the radiosonde data from a station over the Indian west coast and IMERG precipitation product, we show that climatologically, these phases can be mapped over an Fr-based classification of the monsoonal westerly flow. Classifying the flow as 'High Fr' (Fr &gt;1), 'Moderate Fr' ( 0.5 &lt; Fr &amp;#8804; 1) and 'Low Fr' ( Fr &amp;#8804; 0.5 ) gives three topographical modes of precipitation -- 'Orographic', 'Coastal' and 'Offshore', respectively. &amp;#160;Moreover, these modes are not sensitive to the choice of radiosonde station over the west coast.&lt;/p&gt;

scholarly journals Summer Monsoon Season Streamflow Variations in the Middle Yellow River since 1570 CE Inferred from Tree Rings of Pinus tabulaeformis

Atmosphere ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 717 ◽  
Author(s):  
Feng Chen ◽  
Magdalena Opała-Owczarek ◽  
Piotr Owczarek ◽  
Youping Chen
Keyword(s):  
Tree Rings ◽  
Summer Monsoon ◽  
Yellow River ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Pinus Tabulaeformis ◽  
The Yellow River ◽  
Summer Monsoon Season ◽  
Streamflow Reconstruction ◽  
Asian Summer

This study investigates the potential reconstruction of summer monsoon season streamflow variations in the middle reaches of the Yellow River from tree rings in the Qinling Mountains. The regional chronology is significantly positively correlated with the July–October streamflow of the middle Yellow River from 1919 to 1949, and the derived reconstruction explains 36.4% of the actual streamflow variance during this period. High streamflows occurred during 1644–1757, 1795–1806, 1818–1833, 1882–1900, 1909–1920 and 1933–1963. Low streamflows occurred during 1570–1643, 1758–1794, 1807–1817, 1834–1868, 1921–1932 and 1964–2012. High and low streamflow intervals also correspond well to the East Asian summer monsoon (EASM) intensity. Some negative correlations of our streamflow reconstruction with Indo-Pacific sea surface temperature (SST) also suggest the linkage of regional streamflow changes to the Asian summer monsoon circulation. Although climate change has some important effects on the variation in streamflow, anthropogenic activities are the primary factors mediating the flow cessation of the Yellow River, based on streamflow reconstruction.

IMDAA Regional Reanalysis: Performance Evaluation During Indian Summer Monsoon Season

2020 ◽  
Vol 125 (2) ◽  
Author(s):  
Raghavendra Ashrit ◽  
S. Indira Rani ◽  
Sushant Kumar ◽  
S. Karunasagar ◽  
T. Arulalan ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Monsoon Season ◽  
Summer Monsoon Season ◽  
Regional Reanalysis
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