Monsoon Onset Research Articles

Influence of varieties and sowing dates on growth and yield of kharif groundnut (Arachis hypogaea L.)

A field experiment was conducted to study the Influence of varieties and sowing dates on growth and yield of kharif groundnut (Arachis hypogaea L.) at Anand Agricultue University, Anand, during kharif season of 2019 and 2020. The treatments consisted of three dates of sowing viz; first date of sowing - onset of monsoon, second date of sowing - 10 days after onset of monsoon and third date of sowing - 20 days after onset of monsoon with three varieties viz; GG 20, GJG 34 and TAG 37A. The experiment was replicated four times in randomized block design (factorial). Results showed that first date of sowing (onset of monsoon) proved significantly superior to other dates of sowing in respect of growth and yield characters. Significantly high pod yield (2176 kg ha-1 and 1862 kg ha-1) was recorded during 2019 and 2020 under first date of sowing, respectively which was statistically at par with second date of sowing (1937 kg ha-1 and 1592 kg ha-1) and significantly higher than the third date of sowing (1614 kg ha-1 and 1369 kg ha-1). In case of crop sown at onset of monsoon, rainfall, soil moisture and mean temperature favorable during crop growing period showed significantly higher pod yield. Among the varieties, significantly higher pod yield (2043 and 1701 kg ha-1) was recorded under GG 20 over other varieties GJG 34 and TAG 3A during both the years. Hence, variety GG 20 was the promising ones in terms of growth and yield in middle Gujarat agro climatic zone. On an average, onset of monsoon (early sowing) gave 13.4% higher pod yield than 10 days after onset of monsoon sowing. GG 20 was recorded 6.8 % higher pod yield as compared to the GJG 34.

Influence of varieties and sowing dates on growth and yield of kharif groundnut (Arachis hypogaea L.)

A field experiment was conducted to study the Influence of varieties and sowing dates on growth and yield of kharif groundnut (Arachis hypogaea L.) at Anand Agricultue University, Anand, during kharif season of 2019 and 2020. The treatments consisted of three dates of sowing viz; first date of sowing - onset of monsoon, second date of sowing - 10 days after onset of monsoon and third date of sowing - 20 days after onset of monsoon with three varieties viz; GG 20, GJG 34 and TAG 37A. The experiment was replicated four times in randomized block design (factorial). Results showed that first date of sowing (onset of monsoon) proved significantly superior to other dates of sowing in respect of growth and yield characters. Significantly high pod yield (2176 kg ha-1 and 1862 kg ha-1) was recorded during 2019 and 2020 under first date of sowing, respectively which was statistically at par with second date of sowing (1937 kg ha-1 and 1592 kg ha-1) and significantly higher than the third date of sowing (1614 kg ha-1 and 1369 kg ha-1). In case of crop sown at onset of monsoon, rainfall, soil moisture and mean temperature favorable during crop growing period showed significantly higher pod yield. Among the varieties, significantly higher pod yield (2043 and 1701 kg ha-1) was recorded under GG 20 over other varieties GJG 34 and TAG 3A during both the years. Hence, variety GG 20 was the promising ones in terms of growth and yield in middle Gujarat agro climatic zone. On an average, onset of monsoon (early sowing) gave 13.4% higher pod yield than 10 days after onset of monsoon sowing. GG 20 was recorded 6.8 % higher pod yield as compared to the GJG 34.

Understanding the Physical Processes in Indian Monsoon Onset Extremes

Understanding the Physical Processes in Indian Monsoon Onset Extremes

Interannual Variation in Moisture Sources for the First Rainy Season in South China Estimated by the FLEXPART Model

Abstract The first rainy season (April–June) of South China includes the phases before and after the onset of the South China Sea summer monsoon (SCSSM). Abundant moisture supply is the key dynamic process for precipitation formation. Thus, we employ the FLEXPART model to explore the corresponding moisture sources for the two phases. Before the onset of SCSSM, land regions contribute more moisture to the precipitation over South China than the ocean sources. The main source regions are Southeast Asia (27.01%), the South China Sea (25.96%), South China (11.12%), and the southern part of the northwestern Pacific (10.23%). Land sources (66.87%) play a more important role than ocean sources (33.13%) in the interannual variations, with the contributions mainly from Southeast Asia (47.56%) and the South China Sea (28.79%). After the onset of SCSSM, the climatological contribution of ocean sources is larger than that of land regions, and the main source regions are the South China Sea (20.78%), Southeast Asia (17.51%), the Bay of Bengal (13.76%), and South China (11.21%). For the interannual variations, the contributions of land sources and ocean regions are comparable, and mainly from Southeast Asia (33.53%) and the Bay of Bengal (32.26%). The moisture transports for the interannual variations in first rainy season precipitation over South China before and after the onset of SCSSM are significantly correlated with the east–west contrast of sea surface temperature anomalies over northern part of North Pacific and the uniform warming over Indian Ocean, respectively. This study provides important guidance in improving the regional precipitation predictions and understanding the water resources changes.

A Subseasonal Regime Approach for Assessing Intra-annual Variability of Evapotranspiration and Application to the Upper Colorado River Basin

Evapotranspiration (ET) is strongly influenced by gradual climate change and fluctuations in meteorological conditions, such as earlier snowmelt and occurrence of droughts. While numerous studies have investigated how climate change influences the inter-annual variability of ET, very few studies focused on quantifying how subseasonal events control the intra-variability of ET. In this study, we developed the concept of subseasonal regimes, whose timing and duration are determined statistically using Hidden Markov Models (HMM) based on meteorological conditions. We tested the value of subseasonal regimes for quantitatively characterizing the variability of seasonal and subseasonal events, including the onset of snow accumulation, snowmelt, growing season, monsoon, and defoliation. We examined how ET varied as a function of the timing of these events within a year and across six watersheds in the region. Variability of annual ET across these six sites is much less significant than the variability in hydroclimate attributes at the sites. Subseasonal ET, defined as the total ET during a given subseasonal regime, provides a measure of intra-annual variability of ET. Our study suggests that snowmelt and monsoon timing influence regime transitions and duration, such as earlier snowmelt can increase springtime ET rapidly but can trigger long-lasting fore-summer drought conditions that lead to decrease subseasonal ET. Overall, our approach provides an enhanced statistically based framework for quantifying how the timing of subseasonal-event transitions influence ET variability. The improved understanding of subseasonal ET variability is important for predicting the future impact of climate change on water resources from the Upper Colorado River Basin regions.

The Weakening Relationship between ENSO and the South China Sea Summer Monsoon Onset in Recent Decades

The Weakening Relationship between ENSO and the South China Sea Summer Monsoon Onset in Recent Decades

Assessment of Meteorological Drought using Standard Precipitation Index (SPI) in Western Maharashtra, India

The crop production in rainy season in rainfed areas is dependent on vagaries of monsoon and is adversely influenced. The knowledge of different rainfall characteristics such as onset and withdrawal of monsoon, dry spell and drought would enable the optimal crop planning and implementation of protective irrigation strategies, thus mitigating the adverse impact of uncertainties of rainfall. The assessment of drought is one of the most important steps in risk management of drought analysis. The basis of drought indices is often based on measuring the deviation of precipitation values from long-term mean, during a specific period of time. The standard precipitation index (SPI) can be used for indicating the associated temporal and spatial variations. The aim of this research is the assessment of the characteristics such as intensity of meteorological drought using SPI with 12 months time scales in Western Maharashtra, India. The index has been computed in with 12 months time scales for 105 stations with 30 years record period in the study area and evaluated for the recent drought during 1983-2012. The results indicate that the rainfall pattern of Western Maharashtra exhibits non-uniform, irregular and erratic pattern of rainfall, as evidenced from SPI values. The meteorological drought shifted one step towards severity of drought condition for the time scales (month 1-12) i.e. from extremely wet to very wet; very wet to moderately wet; moderately wet to near normal; near normal to moderately dry; moderately dry to severely dry and severely dry to extremely dry condition.

Agro Advisories a Boon for Crop Planning on Real Weather Basis in Scaracity Zone of Maharashtra

More than 70% of farms in Scarcity Zone of Maharashtra are small and marginal and are thus vulnerable to climate variability. Some factors, such as increased temperatures and longer droughts periods, are likely to depress production. Managing climate risks is a major challenge of today and for the future. To extend the period of forecast for 3-7 days i.e., medium range weather forecast for the benefit of farming, community the India Meteorological Department has been issuing district level medium range forecast to the 127 agrometeorological field units in the country. Under this project apart from weather forecasts, agro-advisories based on weather are also being issued for the benefit of farming community by the AMFU’s. Advisories are farmers bulletin, which take into account the prevailing weather, soil and crop condition, weather forecasts and, suggest measures to minimize the losses (crop or livestock) and effective utilization of inputs (irrigation, fertilizers pesticides etc.,) and also suggest contingent crop planning.The following points are to be kept in mind for preparing effective agro-advisory bulletins:Identification of weather sensitive field operations, Accurate weather forecast taking into cognizance local weather. Real time information on crops (major crops, varieties, sowing time, phonological stage, status of pests and diseases etc.). Reliable source of information .Crop weather calendars, easily understandable language.The feedback is collected from the contact progressive farmers, on usefulness of the advisories as well as suggestions for its improvements. Systemtic study conducted by this unit on economic impact of the project in six villages in Solapur District revealed that there is a benefit of 12- 23% due to adoption of agromet advisories. The contingency plans are needed if following conditions prevail :Failure of south-West Monsoon, Delayed onset or early withdrawal of monsoon, Deficit or erratic rainfall, Damage to crops due to cyclones floods etc. Crop loss due to droughts, Insufficient supply of irrigation water or late release of canal water, Long dry spells, Heat or cold waves, Severe pest or disease outbreaks due to favorable weather conditions.Medium range weather forecast is useful in issuing location specific weather based Agro-advisors to tailor the agricultural operations. By closely monitoring seasonal conditions and using medium range weather forecast an effective contingency cropping strategy is possible. Timely dissemination of these advisories/ contingency crop plans/measures will help the farmers to maximize the yield by optimum use of inputs and enhance the economic returns of the farmers.

Block-wise Estimation of Rainfall Variability in District Sawai Madhopur, Rajasthan

The present research investigation was undertaken to work out the rainfall variability estimation of different blocks of Sawai madhopur district, Rajasthan. The coefficient of variation and standard deviation for weekly, monthly and annual rainfall were computed for all the five blocks. The normal onset of monsoon in Sawai madhopur district is between June to September. It was found that annual rainfall is higher at Sawai madhopur block during last three decade followed by Gangapur and Khandar block. The mean annual rainfall is lowest in Bonli block. When the CV for the annual rainfall was examined, it was found be the least in Gangapur block, followed by Khandar, Bonli, Bamanwas and it was the highest in Sawai madhopur block.

Relative Roles of Intraseasonal and Above-seasonal Components in the South China Sea Summer Monsoon Onset

Relative Roles of Intraseasonal and Above-seasonal Components in the South China Sea Summer Monsoon Onset

Response of Sea Surface Energy Fluxes To the South China Sea Summer Monsoon Onset in 2021

Response of Sea Surface Energy Fluxes To the South China Sea Summer Monsoon Onset in 2021

Investigation of Atmospheric Boundary Layer characteristics using Ceilometer Lidar, COSMIC GPS RO satellite, Radiosonde and ERA-5 reanalysis dataset over Western Indian Region

Atmospheric Boundary Layer (ABL) characteristics are investigated using a Ceilometer Lidar over Ahmedabad, a semi-arid region in western India. Strong diurnal variations of ABL are observed during 2019, the observation period. There is a stark winter-summer difference in ABL, with summer Boundary Layer Height (BLH) exceeding winter BLH by 1–1.5 km. ABL usually collapses during monsoon and is equivocal due to the presence of thick clouds on top of ABL. The ABL is thicker during the onset of monsoon in contrast to active monsoon, rises again during the withdrawal of monsoon. Lidar observed ABL has been compared with satellite, radiosonde, and European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5) dataset. ERA5 shows good agreement with differences within 500 m; radiosonde observations have under-estimated ground-based measurements, especially during summer. Satellite observations highly overestimated BLH. This comparative study reveals the importance of ground-based lidars in continuous monitoring of ABL at high resolution because radiosonde, satellite, and reanalysis datasets have coarser resolutions and sparse observations. Such quantitative evaluation of ABL is formerly unavailable over this region, which can now be used to improve the representation in numerical models and thereby estimates of radiative and climate effects due to ABL.

Convection Initiation at a Coastal Rainfall Hotspot in South China: Synoptic Patterns and Orographic Effects

AbstractThis study documents the detailed features and processes of convection initiation (CI) at a coastal rainfall hotspot in South China, with emphasis on the typical meteorological conditions and effects of small‐scale orography. The CI occurrences are identified using high‐quality radar mosaics during 7‐year warm seasons. They tend to maximize in low‐lying areas adjacent to coastal small‐scale mountains rather than on the windward slopes of major mountains as previously expected. The genesis of the coastal convection exhibits a remarkable diurnal peak in the early afternoon and mostly occurs on the days of low‐level southwesterlies with a jet‐nose structure in offshore region. These onshore flows enhance the low‐level moistening and convergence on coasts. The characteristic synoptic patterns become common after the onset of summer monsoon, suggesting the key role of monsoonal flows in triggering coastal convection. Driven by the atmospheric conditions of the dominant synoptic pattern, quasi‐idealized numerical simulations demonstrate that the coastal small‐scale mountains disturb the low‐level onshore flow and produce multiple enhanced convergent zones downstream of the mountains. The induced local variations in upward motion and moisture pooling explain the CI occurrences that are located close to these small‐scale mountains. When these mountains are artificially removed in the simulation, convection preferentially initiates on the windward slopes of major mountains as expected. The findings suggest that the small‐scale orography can strongly regulate the local patterns of CI hotspot through disturbing low‐level onshore flow. An explicit resolving of the small‐scale coastal orography is warranted to improve the modeling of local severe weather.

Subseasonal Predictability of South China Sea Summer Monsoon Onset With the ECMWF S2S Forecasting System

AbstractAccurate forecasting of the South China Sea summer monsoon (SCSSM) onset is critical for water resource management in the rainy season across East Asia. The present work evaluates the skill of the ECMWF subseasonal‐to‐seasonal (S2S) forecasting system in predicting SCSSM onset dates using a hindcast experiment. The model provides accurate predictions of the SCSSM onset date 10 days in advance. The predictability mainly arises from the sea surface temperature anomaly (SSTA) in the northern Indian Ocean and central‐eastern tropical Pacific, which usually coincides with moderate and extreme decaying El Niño, thus creating windows of opportunity for SCSSM onset forecasting. The model can reasonably reproduce the SCSSM‐related SSTA and its induced atmospheric teleconnections. However, when anomalous Ural blocking influences the mid‐high latitudes, the ECMWF model forecasts of the SCSSM onset are trapped in the synoptic timescale because of the limited ability of the model to consider blocking in forecasting.

Stable Isotopes in Precipitation and Meteoric Water: Sourcing and Tracing the North American Monsoon in Arizona, New Mexico, and Utah

AbstractThe North American Monsoon (NAM) is an important source of precipitation across the southwestern United States. The approximate northern boundary of this feature crosses the Navajo Nation (NN), in the Four Corners region, where NAM rains have long been important to the livelihoods of Native Americans. Relatively little is known about the characteristics and hydrological significance of the NAM in this region. Here, we report a new 4 yr record of stable H and O isotope ratios in monsoon‐season rainfall and water resources across the NN. Monthly precipitation samples collected at 39 sites document a characteristic pattern of 2H‐ and 18O‐enrichment associated with monsoonal precipitation. These changes are weakly correlated with local precipitation amount, however, and the correlation that does exist is dominated by sub‐cloud evaporation effects. In contrast to precipitation amount, monsoon‐season isotopic values exhibited little spatial variability across the region, and after correction for sub‐cloud evaporation NN values were similar to those from a site in southern Arizona. Airmass back trajectory analysis suggests that the uniformly high NAM precipitation water isotope ratios across the region may reflect (a) a region‐wide shift from mid‐latitude to low‐latitude moisture sources at the onset of the peak monsoon, and (b) substantial land‐surface recycling of NAM moisture in upwind regions. Comparison of precipitation water isotope data with surface and groundwater values implies that, despite its hydroclimatic significance, monsoon rainfall contributes little to subsurface water resources. This highlights the monsoon's importance for warm‐season land‐surface ecology and hydrology critical to residents in the Four Corners region.

Impact of Climate Change on Milk Production and Perceptions of Farmers in the West Bengal

The cause and effect relationship of climatic variables on milk production of indigenous cattle and buffalo had been carried in West Bengal state during 2019-2020. Regression analysis indicated the indigenous cow milk production was directly responsive to annual minimum temperature, while crossbred cow milk production was indirectly responsive to annual maximum temperature and relative humidity. The buffalo milk production was inversely related to annual maximum temperature and relative humidity. More than half of surveyed farmers had a medium level of experience in farming. Majority of farmers were perceived climate variability in general like increase in temperature during the summer season, late onset of monsoon and early withdrawal of monsoon season. For crop farming, crop diversification was the most preferred adaptation strategy among the farmers followed by changing crop variety. For dairy farming, provide proper shed and shelter was most preferred adaptation strategy followed by provide additional fresh drinking water in summer.

Increasing incidence of Arabian Sea cyclones during the monsoon onset phase: Its impact on the robustness and advancement of Indian summer monsoon

During recent decades, the Arabian Sea witnessed frequent occurrences of cyclones during the onset phase of the Indian Summer Monsoon. This study examined the impact of these cyclones on the establishment and northward propagation of the monsoon system. The main dynamical components of the monsoon semi-permanent systems, including wind at 850 hPa and 150 hPa, are analysed separately for Arabian Sea Cyclone Years (ACY) and Non-Cyclone Years (NCY). Pentad (5-day average) composites for ACY and NCY are prepared with respect to pentads centred on monsoon onset date over Kerala (MOK). Six pentad composites (2 before; 1 during and 3 after the onset pentad) are prepared to examine the evolution of the monsoon system over the Indian region. The analysis shows that LLJ and TEJ have been altered by the cyclones formed within ±8 days of monsoon onset over Kerala. For ACY, the LLJ and TEJ patterns require 10 days to stabilise into (acquire) its normal pattern (spatial and intensity) as NCY. Pentad (similar) analysis of SST also shows a consistent pattern to that of LLJ. As the speed of LLJ increases, the SST decreases along the path of LLJ. Total Precipitable Water shows a significant change over the Arabian Sea rather than the Bay of Bengal on the day of onset and thereafter. The changes in the upper tropospheric meridional temperature gradient are responsible for TEJ alteration. Cyclone-induced perturbations are found to disturb the thermodynamical and dynamical state of the background monsoon circulation. The high value of vertical wind shear of zonal wind over the Indian Monsoon area during NCY is ideal for monsoon and arises due to strong LLJ and TEJ. The north-south temperature difference is less for ACY, which leads to a slight delay in establishing TEJ after the onset of monsoon. Kinetic energy at 925 hPa level is higher during NCY than ACY and is supporting the rainfall variations.

Summer monsoon onset over Andaman & Nicobar Islands: Objective criteria for operational forecaster

Summer monsoon onset over Andaman & Nicobar Islands: Objective criteria for operational forecaster

Analysis of rainfall characteristics and moisture availability index for crop planning in semi arid region of north Gujarat

The rainfall, one of the most important natural input resource for dryland agricultural production system, is erratic and temporal in nature. An attempt has been made to analyze thirty years (1990-2019) of meteorological data for prediction of probable week of onset and withdrawal of monsoon and to end with crop planning in North Gujarat region (India).The highest and lowest amount of weekly rainfall was observed in 27th and 39th SMW, respectively. The probability distribution functions viz. generalized extreme value, Gumbel maximum, Gamma and Weibull were found best-fit for prediction of weekly rainfall. The analysis revealed 26th SMW (25 Jun – 01 Jul) and onwards as the most suited sowing time of kharif crops. There are also chances of occurrence of moisture stress during 34th and 35th SMW. The results would be useful for agricultural scientists, researchers, decision makers and policy planners in the field of agricultural crop planning and irrigation management for semi arid regions.

Evolution of South China Sea and East Asian monsoon from spring to summer by the progression of daily weather types

AbstractThe monsoon development in the early rainy season in East Asia is analysed by the evolution of daily weather types (WTs). The WTs are classified by a k‐means clustering analysis based on 850 hPa winds from April 1 to July 31 in the 40‐year period of 1979–2018. Five WTs are identified, typifying the progression of weather regimes in the monsoonal evolution. WTs 1 and 2, with easterly winds in the South China Sea (SCS), occurs mostly in April and early May, corresponding to typical WTs before the SCS monsoon onset. In WT3, winds in the SCS turns westerly, and a rain band emerges in South China, extending east‐northeastward to the Pacific Ocean south of Japan, which signifies the May–June Mei‐yu in South China. Then, with the rain band moved to Yangtze River Valley (YRV) in WT4, this WT corresponds to the June–July Mei‐Yu in central and eastern China along the YRV. Finally, WT5 occurs more frequently towards the end of July, and corresponds to the post‐Mei‐Yu WT, indicating the ending of the early summer rainfall season in East Asia. The evolution of the WTs is gradual but intermittent, representing the weather‐within‐climate information. Each WT likely persists to itself. But WT1 and WT2 also progress to each other. The long persistence of WT3 and WT4 up to several weeks indicates the quasi‐stationary Mei‐Yu in South China and the YRV, respectively. The year‐to‐year variability of the WTs is also evident in the WTs. The El Niño–Southern Oscillation (ENSO) impact on the precipitation in the East Asian region is analysed for three types of ENSO: Eastern Pacific, Central Pacific, and mixed El Niño and La Niña. The seasonal mean precipitation anomalies can be interpreted by the frequencies of the daily WTs under different ENSO conditions.