scholarly journals Breaks in monsoon and related precursors

MAUSAM ◽  
2022 ◽  
Vol 53 (3) ◽  
pp. 309-318
Author(s):  
U. S. DE ◽  
R. K. MUKHOPADHYAY
Keyword(s):  
Daily Rainfall ◽  
Equatorial Region ◽  
Wave Radiation ◽  
Large Area ◽  
Time Section ◽  
Middle Troposphere ◽  
Latitudinal Belt ◽  
Anomaly Pattern ◽  
Rainfall Departure ◽  
Normal Rainfall

A comprehensive analysis of eleven break monsoon situations that occurred during the period 1987 to 1997 have been attempted in the study. The various features like daily rainfall departures, wind anomalies and the satellite derived Outgoing Long wave Radiation (OLR) associated with the commencement/cessation of the break monsoon condition are studied with a view to identifying the precursors associate the break situation. The results reveal that there is progressive decrease  of below normal rainfall departures 5 days prior to the actual break day in the latitude belts south of 20° N. During the period of the revival of the monsoon, the time section of the daily rainfall departures shows that the daily rainfall departure first starts becoming above normal in the southern most latitudinal belt 5° N to 10°N from the second day onwards after the cessation of the break. Similarly, the easterly anomalies in the zonal wind are first noticed in the southern latitude even 5 days prior to the starting of the break in the lower and middle troposphere. The maximum easterly anomalies in the lower and the middle troposphere move northwards upto 20° N. The composite latitudinal time section of OLR anomaly show a large area of negative OLR anomaly extending from 20°S to 10°N. The area is defined as the Southern. Hemispheric Convective Zone ( SHCZ). The negative OLR anomaly (10 Wm-2 is noticed around 5° S to 0° N. It increases to 20 Wm-2 on the second day of the break on the same latitudinal belt. The daily OLR anomaly pattern shows that the area of the negative OLR anomaly around the equatorial region increases with the approach of a break epoch. The forecasting aspects of the commencement / cessation of the break have been also discussed.

scholarly journals Regional landslide forecasting in Piemonte (Italy) and in Norway: experiences from 2013 late spring

2017 ◽  
Author(s):  
Davide Tiranti ◽  
Graziella Devoli ◽  
Roberto Cremonini ◽  
Monica Sund ◽  
Søren Boje
Keyword(s):  
National Level ◽  
Daily Rainfall ◽  
Landslide Hazard ◽  
Weather Type ◽  
Late Spring ◽  
Large Area ◽  
Pressure System ◽  
Weather System ◽  
Landslide Forecasting ◽  
Hazard Assessments

Abstract. A few countries in the world operate systematically national and regional forecasting services for rainfall-induced landslides (i.e. shallow landslides, debris flows and debris avalanches), among them: Norway and Italy. In Norway, the Norwegian Water Resources and Energy Directorate (NVE) operates a landslide forecasting service at national level. A daily national hazard assessment is performed, describing both expected awareness level and type of landslide hazard for a selected warning region. In Italy, each administrative region has its own regional environmental agency (Regional Agency for Environmental Protection, ARPA) that is responsible of the daily landslide hazard assessments and emission of landslide warnings for one or more catchments within the region. One of these agencies, the ARPA Piemonte, is responsible for issuing landslide warnings for the Piemonte region, located in Northwestern Italy. Both services provide regular landslide hazard assessments founded on a combination of quantitative thresholds and daily rainfall forecasts together with qualitative expert analysis. Daily warning reports are published at http://www.arpa.piemonte.gov.it/rischinaturali and www.varsom.no. On spring 2013, the ARPA Piemonte, and the NVE issued warnings for hydro-meteorological hazards due to the arrival of a deep and large low-pressure system, called herein Vb cyclone. This kind of weather system is known to produce the largest floods in Europe. Less known is that the weather type can trigger landslides as well. In this study, we present the experiences acquired in late spring 2013 by NVE and ARPA Piemonte. From 27th April to 19nd May 2013, more than 400 mm rain in Piemonte caused severe floods and diffused landslides. In Norway, the same weather type lasted from 15th May to 2nd June 2013 and brought warm winds with high temperatures that caused intense snow melt over a large area, and brought a lot of rain in the Southeastern Norway, initiating large flood along Glomma river and several landslides. Floods and landslides produced significant damages to roads and railways along with buildings and other infrastructure in both countries.

scholarly journals Long-distance radiation of Rossby waves from the equatorial current system

2021 ◽  
Author(s):  
J. Thomas Farrar ◽  
Theodore Durland ◽  
Steven R. Jayne ◽  
James F. Price
Keyword(s):  
Rossby Waves ◽  
Current System ◽  
Kamchatka Peninsula ◽  
Equatorial Region ◽  
Wave Radiation ◽  
Long Distance ◽  
Instability Waves ◽  
Tropical Instability Waves ◽  
The North ◽  
Equatorial Current

AbstractMeasurements from satellite altimetry are used to show that sea-surface height (SSH) variability throughout much of the North Pacific is coherent with the SSH signal of the tropical instability waves (TIWs) that result from instabilities of the equatorial currents. This variability has regular phase patterns consistent with freely propagating barotropic Rossby waves radiating energy away from the unstable equatorial currents, and the waves clearly propagate from the equatorial region to at least 30°N. The pattern of SSH variance at TIW frequencies exhibits remarkable patchiness on scales of hundreds of kilometers, which we interpret as being due to the combined effects of wave reflection, refraction, and interference. North of 40°N, more than 6000 km from the unstable equatorial currents, the SSH field remains coherent with the near-equatorial SSH variability, but it is not as clear whether the variability at the higher latitudes is a simple result of barotropic wave radiation from the tropical instability waves. Even more distant regions, as far north as the Aleutian Islands off of Alaska and the Kamchatka Peninsula of eastern Russia, have SSH variability that is significantly coherent with the near-equatorial instabilities. The variability is not well represented in the widely used gridded SSH data product commonly referred to as the AVISO or DUACS product, and this appears to be a result of spatial variations in the filtering properties of the objective mapping scheme.

scholarly journals A statistical technique for determination of withdrawal of northeast monsoon over coastal Tamilnadu

MAUSAM ◽  
2021 ◽  
Vol 49 (3) ◽  
pp. 309-320
Author(s):  
Y. E. A. RAJ
Keyword(s):  
Standard Deviation ◽  
Tamil Nadu ◽  
Daily Rainfall ◽  
Statistical Technique ◽  
Northeast Monsoon ◽  
Dynamic Features ◽  
Superposed Epoch Analysis ◽  
Average Decrease ◽  
Sole Criterion ◽  
Normal Rainfall

The withdrawal dates of northeast monsoon over coastal Tamil Nadu for the 90-year period (1901-90) have been objectively derived. The methodology of determination was generally based on an index based on the spatial distribution of daily rainfall over stations of coastal Tamil Nadu, over a 5-day pentad for the six month period, September- February. The normal withdrawal date thus obtained was 27 December with a standard deviation of 13.6 days and range 23 November-28 January. The duration of northeast monsoon was distributed with mean 67.5 days, standard deviation 14.9 days and range 26-102 days. During 36.7 % of years the withdrawal spilled over to January of next year. The daily normal rainfall and its difference filter have been discussed with reference to the normal date of withdrawal. The average decrease of rainfall at the time of withdrawal has been derived by application of superposed epoch analysis. It has further been shown that during years when the withdrawal took place in January the intensity of northeast monsoon prior to withdrawal was as intense as in years when withdrawal occurred in December. A few cases of northeast monsoon withdrawal have been illustrated with diagrams. As no definite dynamic or thermodynamic features could be uniquely identified which are associated with the withdrawal, this technique is basically statistical, considering the behaviour of the daily normal rainfall as the sole criterion. Unique thermodynamic and dynamic features are not identifiable which are associated with the withdrawal of northeast monsoon over coastal Tamilnadu.

scholarly journals Study of rainfall departure over catchments of Bihar plains

MAUSAM ◽  
2021 ◽  
Vol 61 (2) ◽  
pp. 187-196
Author(s):  
T. N. JHA ◽  
R. D. RAM
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Monsoon Season ◽  
Daily Rainfall ◽  
La Niña ◽  
Rainfall Time Series ◽  
La Nina ◽  
Multivariate Enso Index ◽  
Rainfall Departure

Station wise daily rainfall data of sixty years is used to study rainfall departure and variability  in  Kosi, Kamala/Bagmati/Adhwara and  Gandak/Burhi Gandak catchments during  monsoon  season. Station and catchment wise rainfall time series have been made to compute rainfall departure and Coefficient of Variation (CV). Southern Oscillation Index (SOI), Multivariate ENSO Index (MEI) and ENSO strength based on percentile analysis are used to ascertain their impact on rainfall distribution in the category as excess, normal, deficient and scanty. Results indicate that the variability is greater over Kosi as compared to the other catchments. Probability of normal rainfall is found 0.75 and there is no possibility of scanty rain over the catchments during El Nino and La Nina year. Similarly probabilities of normal, deficient, excess rainfall are found as 0.67, 0.18 and 0.15 respectively during mixed year. SOI has emerged as principal parameter which modifies the departure during El Nino and La Nina year. MEI along with ENSO strength  are more prominent  during  mixed year  particularly to ascertain deficient and excess rain in weak and strong- moderate La Nina  respectively .   

scholarly journals Indicator-Based Assessment of Drought in Bhilwara District, Rajasthan

2021 ◽  
pp. 141-153
Author(s):  
Gaurav Sharma ◽  
Chandra Kishor Kumar ◽  
Rishi Pathak
Keyword(s):  
Indian Monsoon ◽  
Rainfall Variability ◽  
Daily Rainfall ◽  
Rain Gauge ◽  
Annual Rainfall ◽  
Drought Frequency ◽  
Arid Conditions ◽  
Dry Spells ◽  
Water Scarce ◽  
Rainfall Departure

Management of water resources helps to sustain even in drastic conditions resulted due to unprecedented disruption in rainfall patterns. Change and irregularity in the pattern of the Indian monsoon are the outcomes of human-induced activities. Inadequate water availability affecting various sectors namely domestic, industrial, and agricultural sectors that are dependent upon it. To cope under such drastic conditions adaptability and planning prior to its occurrence plays a significant role. It is under this context, the present study investigated drought characteristics which include drought frequency and severity caused by prolonged dry spells in Bhilwara district, Rajasthan. The district falls in the water-scarce regions with arid to semi-arid conditions and with an average annual rainfall of 658.03 mm. Due to high rainfall variability, the region is frequently subsumed under drought-like conditions. Comprehensive analysis using daily rainfall data from 1973-2018 for 12 rain gauge stations in Bhilwara district has been carried out. Most of the stations were drought-prone assessed by probability analysis using Weibull’s plotting position formula. The departure analysis showed that Kotri station has a maximum drought frequency of 1 in 2 years while other stations were having a drought frequency of 1 in 3 to 4 years. Prioritization of drought-prone stations based on rainfall departure analysis helps to initiate an immediate mitigation process based on the ranking of its proneness. Asind and Bhilwara station with RDI 0.91 has maximum proneness and its calls for effective planning for drought management. Based on seasonal departure analysis it is found that 1980, 1981, 1985, 1987, 2000, 2002, 2008, 2015, and 2017 are drought years. The result has been supplemented using NDVI so that the vegetation condition can also be assessed during water stress conditions. The study highlighted that the frequency of drought has increased owing due to climate change and thus, poses serious challenges if not tackle adequately.

scholarly journals Impact of Lightning NOx Emissions on Atmospheric Composition and Meteorology in Africa and Europe

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1128
Author(s):  
Laurent Menut ◽  
Bertrand Bessagnet ◽  
Sylvain Mailler ◽  
Romain Pennel ◽  
Guillaume Siour
Keyword(s):  
Surface Flux ◽  
Short Wave ◽  
Atmospheric Composition ◽  
Wave Radiation ◽  
Nox Emissions ◽  
Large Area ◽  
Convective Clouds ◽  
Pollutant Concentrations ◽  
The Impact ◽  
Lightning Nox

NOx emissions from lightning have been added to the CHIMERE v2020r1 model using a parameterization based on convective clouds. In order to estimate the impact of these emissions on pollutant concentrations, two simulations, using the online coupled WRF-CHIMERE models with and without NOx emissions from lightning, have been carried out over the months of July and August 2013 and over a large area covering Europe and the northern part of Africa. The results show that these emissions modify the pollutant concentrations as well as the meteorology. The changes are most significant where the strongest emissions are located. Adding these emissions improves Aerosol Optical Depth in Africa but has a limited impact on the surface concentrations of pollutants in Europe. For the two-month average we find that the maximum changes are localized and may reach ±0.5 K for 2 m temperature, ±0.5 m s−1 for 10 m wind speed, 10 W m−2 for short wave radiation surface flux, and 50 and 2 μg m−3 for dust and sea salt surface concentrations, respectively. This leads to maximum changes of 1 μg m−3 for surface concentrations of PM2.5.

scholarly journals Characteristics of rainfall pattern for crop planning at Jabalpur region (Madhya Pradesh) of India

MAUSAM ◽  
2021 ◽  
Vol 63 (4) ◽  
pp. 639-644
Author(s):  
K.K. AGRAWAL ◽  
P.K. SINGH
Keyword(s):  
Probability Model ◽  
Daily Rainfall ◽  
Recent Decade ◽  
Madhya Pradesh ◽  
Annual Rainfall ◽  
Growing Period ◽  
Post Monsoon ◽  
Meteorological Observatory ◽  
Normal Rainfall

The daily rainfall data of past 31 years (1978-2008) of Agro meteorological Observatory, Department of Physics & Agriculture Engineering, Jabalpur (Madhya Pradesh) has been analyzed for establishing the long term average of weekly, monthly, seasonal and annual rainfall and its variability. The weekly probability of rainfall was estimated using Markov Chain probability model for receiving >= 10 and 30 mm rainfall per week. The mean annual rainfall observed as 1309 mm and its variability was 27.1 per cent. The highest annual and kharif season rainfall 2083 and 2052 mm respectively were recorded in 1994. On the other hand the lowest annual and kharif rainfall were 620 mm and 471 mm respectively in 1979. The study revealed that the recent decade rainfall has increased during last 31 years. The seasonal average kharif, post monsoon, winter and summer seasons recorded 1197.3 mm, 32.1 mm, 49.8 mm and 29.8 mm of rainfall. About 91.5 per cent of total annual rainfall was received in kharif, 2.5 per cent in post monsoon, 3.8 per cent in winter monsoon and 2.3 per cent in summer. During the period under study 16 per cent of the years recorded excess, 23 per cent deficit and 61 per cent normal rainfall. The July month is regarded as suitable for transplanting of rice crop in Jabalpur region. The highest contribution has been observed in August (33 per cent). Standard week from 25 to 37 received rainfall more than 30 mm indicating the crop growing period from June 2nd week to September last week.

scholarly journals Warm Cover – Precursory Strong Signals hidden in the Middle Troposphere for Haze Pollution

2021 ◽  
Author(s):  
Xiangde Xu ◽  
Wenyue Cai ◽  
Tianliang Zhao ◽  
Xinfa Qiu ◽  
Wenhui Zhu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Eastern China ◽  
Air Pollutant ◽  
Pollutant Emissions ◽  
Ambient Atmosphere ◽  
Large Area ◽  
Middle Troposphere ◽  
Haze Pollution ◽  
Close Relationship ◽  
Pollution Events

Abstract. Eastern China (EC), located on the downstream region of Tibetan Plateau (TP), is a large area that has become vulnerable to frequent haze. In addition of air pollutant emissions, meteorological conditions were a key inducement for air pollution episodes. Based on the study of the Great Smog of London in 1952 and haze pollution in EC over recent decades, it is found that the abnormal warm cover in the middle troposphere, as a precursory strong signal hidden, could connect to severe air pollution events. The convection and diffusion in the atmospheric boundary layer (ABL) were suppressed by a relatively stable structure of warm cover in the middle troposphere, leading to the ABL height decreases, which were favourable for the accumulation of air pollutants in the ambient atmosphere. The warming TP built the warm cover in the middle troposphere from the plateau to the downstream EC region and even the entire East Asian region. The frequent haze events in EC is connected with a significantly strong warm cover in the interdecadal variability. It is also revealed that a close relationship existed between interannual variations of the TP's heat source and the warm cover hidden in the middle troposphere over EC.

scholarly journals Rainfall Anomalies Pattern in Northwestern Nigeria (NWN)

2021 ◽  
pp. 43-52
Author(s):  
Gbenga Emmanuel Olalere ◽  
Lawan Bulama ◽  
Ahmad Abubakar Umar
Keyword(s):  
Climate Change ◽  
Standardized Precipitation Index ◽  
Sampling Technique ◽  
Rainfall Anomaly ◽  
Rainfall Condition ◽  
Anomaly Pattern ◽  
Dry Conditions ◽  
Rainfall Anomalies ◽  
Normal Rainfall ◽  
North Western

Constant investigation into rainfall anomaly pattern is very crucial as it enables the detection of any departure from normal rainfall condition. When such departure is persistent and statistically significant, it could indicate climate change. This study seeks to investigate anomaly pattern of rainfall in north western Nigeria with the view to determine any extreme departure from established normal rainfall behavior (mean). The study used thirty years (30) rainfall data from 1987 to 2016. The data was obtained from the archives of Nigerian Meteorological Agency (NIMET) for six selected synoptic stations from the region. Purposive sampling technique was adopted in selecting the six synoptic stations given consideration to stations with longer consistent rainfall records. The data was subjected to Standardized Anomalies also known as Standardized Precipitation Index (SPI) to obtain anomaly values. The values were used to plot time series for each station. They were also used to determine the dry or years with drought i.e. negative values and wet or moisture years i.e. positive values. The findings showed that throughout the thirty years period, normal conditions dominated the study area with few pockets of dry conditions. The study concludes that rainfall anomalies pattern in north western Nigeria over the thirty years period under investigation was not too far from normal rainfall conditions.

Convergent Beam Electron Diffraction

1978 ◽  
Vol 36 (3) ◽  
pp. 304-315
Author(s):  
G. Lehmpfuhl
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Crystal Surface ◽  
Diffraction Spot ◽  
Crystal Thickness ◽  
Large Area ◽  
Electron Microscopic ◽  
Additional Information ◽  
Microscopic Investigations

Introduction In electron microscopic investigations of crystalline specimens the direct observation of the electron diffraction pattern gives additional information about the specimen. The quality of this information depends on the quality of the crystals or the crystal area contributing to the diffraction pattern. By selected area diffraction in a conventional electron microscope, specimen areas as small as 1 µ in diameter can be investigated. It is well known that crystal areas of that size which must be thin enough (in the order of 1000 Å) for electron microscopic investigations are normally somewhat distorted by bending, or they are not homogeneous. Furthermore, the crystal surface is not well defined over such a large area. These are facts which cause reduction of information in the diffraction pattern. The intensity of a diffraction spot, for example, depends on the crystal thickness. If the thickness is not uniform over the investigated area, one observes an averaged intensity, so that the intensity distribution in the diffraction pattern cannot be used for an analysis unless additional information is available.

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