Differentiating lightning in winter and summer with characteristics of wind-field and mass-field

Abstract. Lightning in winter (December, January, February, DJF) is rare compared to lightning in summer (June, July, August, JJA) in central Europe. The conventional explanation attributes the scarcity of winter lightning to seasonally low values of variables that create favorable conditions in summer. Here we systematically examine whether different meteorological processes are at play in winter. We use cluster analysis and principal component analysis and find physically meaningful groups in ERA5 atmospheric reanalysis data and lightning data for northern Germany. Two sets of conditions emerged: Wind-field-dominated and mass-field (temperature) dominated lightning conditions. Wind-field type lightning is characterized by increased wind speeds, high cloud shear, large dissipation of kinetic energy in the boundary layer, and moderate temperatures. Clouds are close to the ground and a relatively large fraction of the clouds is warmer than −10 °C. Mass-field type lightning is characterized by increased convective available potential energy (CAPE), the presence of convective inhibition (CIN), high temperatures, and accompanying large amounts of water vapor. Large amounts of cloud-physics variables related to charge separation such as ice particles and solid hydrometeors further differentiate both mass-field and wind-field lightning. Winter lightning is wind-field driven whereas in summer lightning is mostly mass-field driven with a small fraction of cases being wind-field driven. Consequently, typical weather situations for wind-field lightning in the study area in northern Germany are strong westerlies with embedded cyclones. For mass-field lightning, the area is typically on the anticyclonic side of a southwesterly jet.

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Geographic Shift and Environment Change of U.S. Tornado Activities in a Warming Climate

Atmosphere ◽

10.3390/atmos12050567 ◽

2021 ◽

Vol 12 (5) ◽

pp. 567

Author(s):

Zuohao Cao ◽

Huaqing Cai ◽

Guang J. Zhang

Keyword(s):

Wind Shear ◽

Convective Available Potential Energy ◽

Geographic Location ◽

Reanalysis Data ◽

Cyclonic Circulation ◽

Upward Motion ◽

Environment Change ◽

Low Level ◽

High Event ◽

The U.S

Even with ever-increasing societal interest in tornado activities engendering catastrophes of loss of life and property damage, the long-term change in the geographic location and environment of tornado activity centers over the last six decades (1954–2018), and its relationship with climate warming in the U.S., is still unknown or not robustly proved scientifically. Utilizing discriminant analysis, we show a statistically significant geographic shift of U.S. tornado activity center (i.e., Tornado Alley) under warming conditions, and we identify five major areas of tornado activity in the new Tornado Alley that were not identified previously. By contrasting warm versus cold years, we demonstrate that the shift of relative warm centers is coupled with the shifts in low pressure and tornado activity centers. The warm and moist air carried by low-level flow from the Gulf of Mexico combined with upward motion acts to fuel convection over the tornado activity centers. Employing composite analyses using high resolution reanalysis data, we further demonstrate that high tornado activities in the U.S. are associated with stronger cyclonic circulation and baroclinicity than low tornado activities, and the high tornado activities are coupled with stronger low-level wind shear, stronger upward motion, and higher convective available potential energy (CAPE) than low tornado activities. The composite differences between high-event and low-event years of tornado activity are identified for the first time in terms of wind shear, upward motion, CAPE, cyclonic circulation and baroclinicity, although some of these environmental variables favorable for tornado development have been discussed in previous studies.

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FOREST DISTURBANCE ANALYSIS WITH LANDSAT-8 OLI DATA RELATED TO A PARAMETRIC WIND FIELD: A CASE STUDY FOR TYPHOON RAMMASUN (201409)

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-3-1629-2018 ◽

2018 ◽

Vol XLII-3 ◽

pp. 1629-1633

Author(s):

C. Tan ◽

W. Fang

Keyword(s):

Remote Sensing ◽

Wind Field ◽

Forest Disturbance ◽

Landsat 8 ◽

Landsat 8 Oli ◽

Dependence Relation ◽

Wind Field Model ◽

Wind Speeds ◽

Sensing Technology ◽

And Function

Forest disturbance induced by tropical cyclone often has significant and profound effects on the structure and function of forest ecosystem. Detection and analysis of post-disaster forest disturbance based on remote sensing technology has been widely applied. At present, it is necessary to conduct further quantitative analysis of the magnitude of forest disturbance with the intensity of typhoon. In this study, taking the case of super typhoon Rammasun (201409), we analysed the sensitivity of four common used remote sensing indices and explored the relationship between remote sensing index and corresponding wind speeds based on pre-and post- Landsat-8 OLI (Operational Land Imager) images and a parameterized wind field model. The results proved that NBR is the most sensitive index for the detection of forest disturbance induced by Typhoon Rammasun and the variation of NBR has a significant linear dependence relation with the simulated 3-second gust wind speed.

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Cloudburst events observed over Uttarakhand during monsoon season 2017 and their analysis

MAUSAM ◽

10.54302/mausam.v73i1.5084 ◽

2022 ◽

Vol 73 (1) ◽

pp. 91-104

Author(s):

BIKRAM SINGH ◽

ROHIT THAPLIYAL

Keyword(s):

Flash Flood ◽

Monsoon Season ◽

Convective Available Potential Energy ◽

Precipitable Water ◽

Interval Data ◽

Rain Gauge ◽

Thermodynamic Conditions ◽

North Pakistan ◽

June July ◽

Head Bay Of Bengal

Cloudburst is an extreme weather event characterised by the occurrence of a large amount of rainfall over a small area within a short span of time with a rainfall of 100 mm or more in one hour. It is responsible for flash flood, inundation of low lying areas and landslides in hills causing extensive damages to life and property. During monsoon season 2017 five number of cloudburst events are observed over Uttarakhand and analysed. Self Recording Rain Gauge (SRRG) and 15 minutes interval data from the newly installed General Packet Radio Service (GPRS) based Automatic Weather Station (AWS) are able to capture the cloudburst events over some areas in Uttarakhand. In this paper, an attempt has been made to find out the significant synoptic and thermodynamic conditions associated with the occurrence of the cloudburst events in Uttarakhand. These 5 cases of cloudburst events that are captured during the month of June, July and August 2017 in Uttarakhand are studied in detail. Synoptically, it is observed that the existence of trough at mean sea level from Punjab to head Bay of Bengal running close to Uttarakhand, the movement of Western Disturbance over north Pakistan and adjoining Jammu & Kashmir and existence of cyclonic circulation over north Rajasthan and neighbourhood are favourable conditions. Also, the presence of strong south-westerly wind flow from the Arabian Sea across West Rajasthan and Haryana on upper air charts are found during these events. Thermodynamically, the Convective Available Potential Energy (CAPE) is found to be high (more than 1100 J/Kg) during most of the cases and vertically integrated precipitable water content (PWC) is more than 55mm. The GPRS based AWS system can help in prediction of the cloud burst event over the specified location with a lead time upto half to one hour in association with radar products.

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Space-time variability of hydrological drought and wetness in Iran using NCEP/NCAR and GPCC datasets

Hydrology and Earth System Sciences ◽

10.5194/hess-14-1919-2010 ◽

2010 ◽

Vol 14 (10) ◽

pp. 1919-1930 ◽

Cited By ~ 21

Author(s):

T. Raziei ◽

I. Bordi ◽

L. S. Pereira ◽

A. Sutera

Keyword(s):

Time Series ◽

Singular Spectrum Analysis ◽

Standardized Precipitation Index ◽

Principal Component ◽

Reanalysis Data ◽

Space Time ◽

Hydrological Drought ◽

Time Variability ◽

Climate Conditions ◽

Good Agreement

Abstract. Space-time variability of hydrological drought and wetness over Iran is investigated using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis and the Global Precipitation Climatology Centre (GPCC) dataset for the common period 1948–2007. The aim is to complement previous studies on the detection of long-term trends in drought/wetness time series and on the applicability of reanalysis data for drought monitoring in Iran. Climate conditions of the area are assessed through the Standardized Precipitation Index (SPI) on 24-month time scale, while Principal Component Analysis (PCA) and Varimax rotation are used for investigating drought/wetness variability, and drought regionalization, respectively. Singular Spectrum Analysis (SSA) is applied to the time series of interest to extract the leading nonlinear components and compare them with linear fittings. Differences in drought and wetness area coverage resulting from the two datasets are discussed also in relation to the change occurred in recent years. NCEP/NCAR and GPCC are in good agreement in identifying four sub-regions as principal spatial modes of drought variability. However, the climate variability in each area is not univocally represented by the two datasets: a good agreement is found for south-eastern and north-western regions, while noticeable discrepancies occur for central and Caspian sea regions. A comparison with NCEP Reanalysis II for the period 1979–2007, seems to exclude that the discrepancies are merely due to the introduction of satellite data into the reanalysis assimilation scheme.

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Can climate models capture the high amplitudes circumglobal waves and their surface imprints?

10.5194/egusphere-egu21-9013 ◽

2021 ◽

Author(s):

Fei Luo ◽

Kai Kornhuber ◽

Frank Selten ◽

Dim Coumou

Keyword(s):

Soil Moisture ◽

Climate Models ◽

Phase Locking ◽

Weather Conditions ◽

Reanalysis Data ◽

Circulation Types ◽

Temperature And Precipitation ◽

Wave Patterns ◽

Precipitation Anomalies ◽

June July

Pronounced circumglobal waves can trigger and maintain persistent summer weather conditions by remaining in their preferred phase-locked positions for several weeks in a row. This phenomenon, especially important for wave numbers 5 and 7, has been observed in recent years, but it is unclear whether climate models can reproduce circulation types and their surface imprints.Here we assess three climate models (EC-Earth3, CESM1.2, and MIROC5) &#160;for their representation of amplified circumglobal waves and associated surface imprints in summer (June, July and August) over 1979-2016. ERA5 reanalysis data is used as reference to assess the models&#8217; performance. We run a series of modeling experiments to understand the source of biases in the climate models: free interactive atmosphere and soil moisture runs (AISI), atmospheric nudged runs (AFSI), soil moisture prescribed runs (AISF), and both atmosphere and soil moisture nudged experiments (AFSF).We show that all models reasonably well reproduce the climatological wave spectra. Further, both wave 5 and wave 7 are found to exhibit phase-locking behaviors across all models, resulting in similar wave patterns across the hemisphere as compared to reanalysis. The surface imprints are observed in the models as well, but depending on the model, the results vary in strength. We also found the biases in surface temperature and precipitation anomalies mainly come from the atmospheric circulation in the models as these biases reduced considerably from AISI runs to AFSI and AFSF runs where upper atmosphere levels were nudged. Nudging soil moisture also minimizes some biases in the models but not as obvious as nudging the atmosphere.&#160;<div> <div> <div>&#160;</div> </div> </div>

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A comparison of Loon balloon observations and stratospheric reanalysis products

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-855-2017 ◽

2017 ◽

Vol 17 (2) ◽

pp. 855-866 ◽

Cited By ~ 16

Author(s):

Leon S. Friedrich ◽

Adrian J. McDonald ◽

Gregory E. Bodeker ◽

Kathy E. Cooper ◽

Jared Lewis ◽

...

Keyword(s):

Reanalysis Data ◽

Location Information ◽

Data Sets ◽

Wind Fields ◽

Weather Forecasts ◽

Wind Speeds ◽

Zonal Winds ◽

Long Duration ◽

Environmental Prediction ◽

Modern Era

Abstract. Location information from long-duration super-pressure balloons flying in the Southern Hemisphere lower stratosphere during 2014 as part of X Project Loon are used to assess the quality of a number of different reanalyses including National Centers for Environmental Prediction Climate Forecast System version 2 (NCEP-CFSv2), European Centre for Medium-Range Weather Forecasts (ERA-Interim), NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA), and the recently released MERRA version 2. Balloon GPS location information is used to derive wind speeds which are then compared with values from the reanalyses interpolated to the balloon times and locations. All reanalysis data sets accurately describe the winds, with biases in zonal winds of less than 0.37 m s−1 and meridional biases of less than 0.08 m s−1. The standard deviation on the differences between Loon and reanalyses zonal winds is latitude-dependent, ranging between 2.5 and 3.5 m s−1, increasing equatorward. Comparisons between Loon trajectories and those calculated by applying a trajectory model to reanalysis wind fields show that MERRA-2 wind fields result in the most accurate simulated trajectories with a mean 5-day balloon–reanalysis trajectory separation of 621 km and median separation of 324 km showing significant improvements over MERRA version 1 and slightly outperforming ERA-Interim. The latitudinal structure of the trajectory statistics for all reanalyses displays marginally lower mean separations between 15 and 35° S than between 35 and 55° S, despite standard deviations in the wind differences increasing toward the equator. This is shown to be related to the distance travelled by the balloon playing a role in the separation statistics.

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Quantification of NOX Emissions Based on Car MAX-DOAS Measurements over Beijing and Impacts of Wind Field

10.5194/egusphere-egu2020-12459 ◽

2020 ◽

Author(s):

Xinghong Cheng

Keyword(s):

Spatial Distribution ◽

Wind Speed ◽

Wind Field ◽

Meteorological Condition ◽

Emission Rates ◽

Wind Fields ◽

Vertical Column ◽

Wind Speeds ◽

South Central ◽

The Mean

We carried out 14 days of Car MAX-DOAS experiments on the 6th Ring Rd of Beijing in January, September and October, 2014. The tropospheric vertical column densities (VCD) of NO2 are retrieved and used to estimate the emissions of NOx. The offline LAPS-WRF-CMAQ model system is used to simulate wind fields by assimilation of observational data and calculate the NO2 to NOx concentration ratios. The NOX emissions in Beijing for different seasons derived from Car MAX-DOAS measurements are compared with the multi-resolution emission inventory in China for 2012 (MEIC 2012), and impacts of wind field on estimated emissions and its uncertainties are also investigated. Results show that the NO2 VCD is higher in January than other two months and it is typically larger at the southern parts of the 6th Ring Road than the northern parts of it. Wind field has obvious impacts on the spatial distribution of NO2 VCD, and the mean NO2 VCD with south wind at most sampling points along the 6th Ring Rd is higher than north wind. The journey-to-journey variation pattern of estimated NOX emissions rates (ENOX) is consistent with that of the NO2 VCD, and ENOX is mainly determined by the NO2 VCD. In addition, the journey-to-journey ENOX in the same month is different and it is affected by wind speed, the ratio of NO2 and NOx concentration and the decay rate of NOX from the emission sources to measured positions under different meteorological condition. The ENOX ranges between 6.46&#215;1025 and 50.05&#215;1025 molec s-1. The averaged ENOX during every journey in January, September and October are respectively 35.87&#215;1025, 20.34&#215;1025, 8.96&#215;1025 molec s-1. The estimated ENOX after removing the simulated error of wind speed and observed deviation of NO2 VCD are found to be mostly closer to the MEIC 2012, but sometimes ENOX is lower or higher and it indicates that the MEIC 2012 might be overestimate or underestimate the true emissions. The estimated ENOX on January 27 and September 19 are obviously higher than other journeys in the same month because the mean NO2 VCD and Leighton ratio during these two periods are larger, and corresponding wind speeds are smaller. Additionally, because south wind may affect the spatial distribution of mean NO2 VCD in Beijing which is downwind of south-central&#160;regions of Hebei province with high source emission rates, the uncertainty of the estimated ENOX with south wind will be increased.

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Improved Tropical-Cyclone Flight-Level Wind Estimates Using Routine Infrared Satellite Reconnaissance

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-14-0112.1 ◽

2015 ◽

Vol 54 (2) ◽

pp. 463-478 ◽

Cited By ~ 25

Author(s):

John A. Knaff ◽

Scott P. Longmore ◽

Robert T. DeMaria ◽

Debra A. Molenar

Keyword(s):

Tropical Cyclone ◽

Principal Components ◽

Wind Field ◽

Motion Vector ◽

Principal Component ◽

Principal Component Method ◽

Tangential Wind ◽

Flight Level ◽

Polar Grid ◽

Single Field

AbstractA new and improved method for estimating tropical-cyclone (TC) flight-level winds using globally and routinely available TC information and infrared (IR) satellite imagery is presented. The developmental dataset is composed of aircraft reconnaissance (1995–2012) that has been analyzed to a 1 km × 10° polar grid that extends outward 165 km from the TC center. The additional use of an azimuthally average tangential wind at 500 km, based on global model analyses, allows the estimation of winds at larger radii. Analyses are rotated to a direction-relative framework, normalized by dividing the wind field by the observed maximum, and then decomposed into azimuthal wavenumbers in terms of amplitudes and phases. Using a single-field principal component method, the amplitudes and phases of the wind field are then statistically related to principal components of motion-relative IR images and factors related to the climatological radius of maximum winds. The IR principal components allow the wind field to be related to the radial and azimuthal variability of the wind field. Results show that this method, when provided with the storm location, the estimated TC intensity, the TC motion vector, and a single IR image, is able to estimate the azimuthal wavenumber 0 and 1 components of the wind field. The resulting wind field reconstruction significantly improves on the method currently used for satellite-based operational TC wind field estimates. This application has several potential uses that are discussed within.

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Wind tunnel tests on the characteristics of wind fields over a simplified gorge

Advances in Structural Engineering ◽

10.1177/1369433216680635 ◽

2016 ◽

Vol 20 (10) ◽

pp. 1599-1611 ◽

Cited By ~ 1

Author(s):

Peng Hu ◽

Yongle Li ◽

Yan Han ◽

CS Cai ◽

Guoji Xu

Keyword(s):

Wind Speed ◽

Wind Tunnel ◽

Wind Direction ◽

Wind Field ◽

Small Range ◽

Wind Fields ◽

Wind Speeds ◽

Mean Wind Speed ◽

Wind Characteristics ◽

The Mean

Characteristics of wind fields over the gorge or valley terrains are becoming more and more important to the structural wind engineering. However, the studies on this topic are very limited. To obtain the fundamental characteristics information about the wind fields over a typical gorge terrain, a V-shaped simplified gorge, which was abstracted from some real deep-cutting gorges where long-span bridges usually straddle, was introduced in the present wind tunnel studies. Then, the wind characteristics including the mean wind speed, turbulence intensity, integral length scale, and the wind power spectrum over the simplified gorge were studied in a simulated atmospheric boundary layer. Furthermore, the effects of the oncoming wind field type and oncoming wind direction on these wind characteristics were also investigated. The results show that compared with the oncoming wind, the wind speeds at the gorge center become larger, but the turbulence intensities and the longitudinal integral length scales become smaller. Generally, the wind fields over the gorge terrain can be approximately divided into two layers, that is, the gorge inner layer and the gorge outer layer. The different oncoming wind field types have remarkable effects on the mean wind speed ratios near the ground. When the angle between the oncoming wind and the axis of the gorge is in a certain small range, such as smaller than 10°, the wind fields are very close to those associated with the wind direction of 0°. However, when the angle is in a larger range, such as larger than 20°, the wind fields in the gorge will significantly change. The research conclusions can provide some references for civil engineering practices regarding the characteristics of wind fields over the real gorge terrains.

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High-resolution global atmospheric moisture connections from evaporation to precipitation

10.5194/essd-2020-89 ◽

2020 ◽

Author(s):

Obbe A. Tuinenburg ◽

Jolanda J. E. Theeuwen ◽

Arie Staal

Keyword(s):

Amazon Basin ◽

Reanalysis Data ◽

Congo Basin ◽

Atmospheric Moisture ◽

Moisture Recycling ◽

Wind Speeds ◽

Complete Dataset ◽

Global Land ◽

Land Recycling ◽

Tracking Model

Abstract. A key Earth system process is the circulation of evaporated moisture through the atmosphere. Spatial connections between evaporation and precipitation affect the global and regional climates by redistributing water and latent heat. Through this atmospheric moisture recycling, land-cover changes influence regional precipitation patterns, with potentially far-reaching effects on human livelihoods and biome distributions across the globe. However, a globally complete dataset of atmospheric moisture flows from evaporation to precipitation has been lacking so far. Here we present a dataset of global atmospheric moisture recycling on both 0.5° and 1.0° spatial resolution. We simulated the moisture flows between each pair of cells across all land and oceans for 2008–2017 and present their monthly climatological means. We applied the Lagrangian moisture tracking model UTrack, which is forced with ERA5 reanalysis data on 25 atmospheric layers and hourly wind speeds and directions. Due to the global coverage of the simulations, a complete picture of both the upwind source areas of precipitation and downwind target areas of evaporation can be obtained. We show a number of statistics of global atmospheric moisture flows: land recycling, basin recycling, mean latitudinal and longitudinal flows, absolute latitudinal and longitudinal flows, and basin recycling for the 26 largest river basins. We find that, on average, 70 % of global land evaporation rains down over land, varying between 62 % and 74 % across the year; 51 % of global land precipitation has evaporated from land, varying between 36 % and 57 % across the year. Highest basin recycling occurs in the Amazon and Congo basins, with evaporation and precipitation recycling of 63 % and 36 % for the Amazon basin and 60 % and 47 % for the Congo basin. These statistics are examples of the potential usage of the dataset, which allows users to identify and quantify the moisture flows from and to any area on Earth, from local to global scales. The dataset is available at https://doi.pangaea.de/10.1594/PANGAEA.912710 (Tuinenburg et al., 2020).

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