scholarly journals Application of Ground-Based Microwave Radiometer in Retrieving Meteorological Characteristics of Tibet Plateau

2021 ◽  
Vol 13 (13) ◽  
pp. 2527
Author(s):  
Jiahua Wei ◽  
Yang Shi ◽  
Yan Ren ◽  
Qiong Li ◽  
Zhen Qiao ◽  
...  
Keyword(s):  
Asian Summer Monsoon ◽  
Microwave Radiometer ◽  
Convective Available Potential Energy ◽  
Precipitable Water ◽  
Atmospheric Temperature ◽  
Precipitation Forecast ◽  
Statistical Characteristics ◽  
Tibet Plateau ◽  
Special Focus ◽  
Sky Conditions

The characteristics of plateau precipitation and atmosphere, once accurately and comprehensively understood, can be used to inform sound air–water resource development practices. In this study, atmospheric exploration of the Tibet Plateau (TP) was conducted using ground-based microwave radiometer (MWR) data collected during the East Asian summer monsoon. Atmospheric temperature, pressure, humidity, and other variables were gathered under clear-sky, cloudy-sky, and rainy-sky conditions. Statistical characteristics of the air parcel height and stability/convection indices such as convective available potential energy (CAPE) and convective inhibition (CIN) were investigated, with a special focus on the rainy-sky condition. Two retrieval applications for characterizing precipitation, namely short-term precipitation forecast and quantitative precipitation estimation were presented. Results showed that CAPE values in the Darlag region reached extremes around 18:00–20:00 (UTC+8) for cloudy-sky and rainy-sky conditions with corresponding peaks of about 1046.56 J/kg and 703.02 J/kg, respectively. When stratiform or convective–mixed precipitation occurs, the precipitable water vapor (PWV) and CAPE values were generally greater than 1.7 cm and 1000 J/kg, respectively. CAPE values are likely to decrease before the occurrence of precipitation due to the release of the latent heat in the atmosphere.

NAM Model Forecasts of Warm-Season Quasi-Stationary Frontal Environments in the Central United States

2010 ◽  
Vol 25 (4) ◽  
pp. 1281-1292 ◽  
Author(s):  
Shih-Yu Wang ◽  
Adam J. Clark
Keyword(s):  
United States ◽  
Mesoscale Model ◽  
Convective Available Potential Energy ◽  
Warm Season ◽  
Correlation Coefficients ◽  
Precipitable Water ◽  
Wind Fields ◽  
Vapor Flux ◽  
Convective Systems ◽  
Central United States

Abstract Using a composite procedure, North American Mesoscale Model (NAM) forecast and observed environments associated with zonally oriented, quasi-stationary surface fronts for 64 cases during July–August 2006–08 were examined for a large region encompassing the central United States. NAM adequately simulated the general synoptic features associated with the frontal environments (e.g., patterns in the low-level wind fields) as well as the positions of the fronts. However, kinematic fields important to frontogenesis such as horizontal deformation and convergence were overpredicted. Surface-based convective available potential energy (CAPE) and precipitable water were also overpredicted, which was likely related to the overprediction of the kinematic fields through convergence of water vapor flux. In addition, a spurious coherence between forecast deformation and precipitation was found using spatial correlation coefficients. Composite precipitation forecasts featured a broad area of rainfall stretched parallel to the composite front, whereas the composite observed precipitation covered a smaller area and had a WNW–ESE orientation relative to the front, consistent with mesoscale convective systems (MCSs) propagating at a slight right angle relative to the thermal gradient. Thus, deficiencies in the NAM precipitation forecasts may at least partially result from the inability to depict MCSs properly. It was observed that errors in the precipitation forecasts appeared to lag those of the kinematic fields, and so it seems likely that deficiencies in the precipitation forecasts are related to the overprediction of the kinematic fields such as deformation. However, no attempts were made to establish whether the overpredicted kinematic fields actually contributed to the errors in the precipitation forecasts or whether the overpredicted kinematic fields were simply an artifact of the precipitation errors. Regardless of the relationship between such errors, recognition of typical warm-season environments associated with these errors should be useful to operational forecasters.

scholarly journals Simulated Sensitivity of Tropical Cyclone Size and Structure to the Atmospheric Temperature Profile

2016 ◽  
Vol 73 (11) ◽  
pp. 4553-4571 ◽  
Author(s):  
Diana R. Stovern ◽  
Elizabeth A. Ritchie
Keyword(s):  
Tropical Cyclone ◽  
Surface Energy ◽  
Temperature Profile ◽  
Convective Available Potential Energy ◽  
Atmospheric Temperature ◽  
Outer Core ◽  
Specific Humidity ◽  
Energy Fluxes ◽  
Surface Energy Fluxes ◽  
Size And Structure

Abstract This study uses the WRF ARW to investigate how different atmospheric temperature environments impact the size and structure development of a simulated tropical cyclone (TC). In each simulation, the entire vertical virtual temperature profile is either warmed or cooled in 1°C increments from an initial specified state while the initial relative humidity profile and sea surface temperature are held constant. This alters the initial amount of convective available potential energy (CAPE), specific humidity, and air–sea temperature difference such that, when the simulated atmosphere is cooled (warmed), the initial specific humidity and CAPE decrease (increase), but the surface energy fluxes from the ocean increase (decrease). It is found that the TCs that form in an initially cooler environment develop larger wind and precipitation fields with more active outer-core rainband formation. Consistent with previous studies, outer-core rainband formation is associated with high surface energy fluxes, which leads to increases in the outer-core wind field. A larger convective field develops despite initializing in a low CAPE environment, and the dynamics are linked to a wider field of surface radial inflow. As the TC matures and radial inflow expands, large imports of relative angular momentum in the boundary layer continue to drive expansion of the TC’s overall size.

scholarly journals A 7-Year Climatology of Warm-Sector Heavy Rainfall over South China during the Pre-Summer Months

Atmosphere ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 914
Author(s):  
Tao Chen ◽  
Da-Lin Zhang
Keyword(s):  
South China ◽  
Heavy Rainfall ◽  
Large Scale ◽  
Convective Available Potential Energy ◽  
Potential Temperature ◽  
Vertical Wind Shear ◽  
Precipitable Water ◽  
Atmospheric Parameter ◽  
Low Level ◽  
Warm Sector

In view of the limited predictability of heavy rainfall (HR) events and the limited understanding of the physical mechanisms governing the initiation and organization of the associated mesoscale convective systems (MCSs), a composite analysis of 58 HR events over the warm sector (i.e., far ahead of the surface cold front), referred to as WSHR events, over South China during the months of April to June 2008~2014 is performed in terms of precipitation, large-scale circulations, pre-storm environmental conditions, and MCS types. Results show that the large-scale circulations of the WSHR events can be categorized into pre-frontal, southwesterly warm and moist ascending airflow, and low-level vortex types, with higher frequency occurrences of the former two types. Their pre-storm environments are characterized by a deep moist layer with >50 mm column-integrated precipitable water, high convective available potential energy with the equivalent potential temperature of ≥340 K at 850 hPa, weak vertical wind shear below 400 hPa, and a low-level jet near 925 hPa with weak warm advection, based on atmospheric parameter composite. Three classes of the corresponding MCSs, exhibiting peak convective activity in the afternoon and the early morning hours, can be identified as linear-shaped, a leading convective line adjoined with trailing stratiform rainfall, and comma-shaped, respectively. It is found that many linear-shaped MCSs in coastal regions are triggered by local topography, enhanced by sea breezes, whereas the latter two classes of MCSs experience isentropic lifting in the southwesterly warm and moist flows. They all develop in large-scale environments with favorable quasi-geostrophic forcing, albeit weak. Conceptual models are finally developed to facilitate our understanding and prediction of the WSHR events over South China.

The dynamics of Holocene monsoon based on meteoric 10Be at Kunlun Pass on the northeastern Qinghai-Tibet Plateau

2021 ◽  
Author(s):  
Peng Chen ◽  
Zhongbo Yu ◽  
Markus Czymzik ◽  
Ala Aldahan ◽  
Jinguo Wang ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Early Holocene ◽  
Tibet Plateau ◽  
The Holocene ◽  
Proxy Records ◽  
Low Levels ◽  
High Level ◽  
Qinghai Tibet Plateau

<p>Multiple proxy records have been used for the understanding of environmental and climate changes during the Holocene. For the first time, we here measure meteoric <sup>10</sup>Be isotope of sediments from a drill core collected at the Kunlun Pass (KP) on the northeastern Qinghai-Tibet Plateau (NETP) to investigate mositure and atmospheric circulation changes during the Holocene. The <sup>10</sup>Be flux suggests relative low levels in the Early Holocene, followed by a sharp increase to high values at around 4 ka BP (4 ka BP = 4000 years before present). Afterwards, the <sup>10</sup>Be flux remains on a high level during the Late Holocene, but decreases slightly towards today. These <sup>10</sup>Be deposition patterns are compared to moisture changes in regions dominated by the Indian Summer Monsoon (ISM), East Asian Summer Monsoon (EASM), and the Westerlies. Different from the gradual changes in monsoon patterns, the <sup>10</sup>Be data reveal low levels during the Early Holocene until ~4 ka BP when an obvious increase was indicated and a relative high level continues to this day, which is relatively more in agreement with patterns of the Westerlies. This finding provides a new evidence for a shift in the dominant pattern of atmospheric circulation at the KP region from a more monsoonal one to one dominated by the Westerlies. Our results improve the understanding of non-stationary interactions and spatial relevance of the EASM, the ISM and the Westerlies on the Qinghai-Tibet Plateau.</p>

scholarly journals Ice Concentration Retrieval from the Analysis of Microwaves: A New Methodology Designed for the Copernicus Imaging Microwave Radiometer

2020 ◽  
Vol 12 (7) ◽  
pp. 1060 ◽  
Author(s):  
Lise Kilic ◽  
Catherine Prigent ◽  
Filipe Aires ◽  
Georg Heygster ◽  
Victor Pellet ◽  
...  
Keyword(s):  
Sea Ice ◽  
Spatial Resolution ◽  
Microwave Radiometer ◽  
Optimal Estimation ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Special Focus ◽  
Polar Regions ◽  
Sea Ice Concentration ◽  
Ice Concentration

Over the last 25 years, the Arctic sea ice has seen its extent decline dramatically. Passive microwave observations, with their ability to penetrate clouds and their independency to sunlight, have been used to provide sea ice concentration (SIC) measurements since the 1970s. The Copernicus Imaging Microwave Radiometer (CIMR) is a high priority candidate mission within the European Copernicus Expansion program, with a special focus on the observation of the polar regions. It will observe at 6.9 and 10.65 GHz with 15 km spatial resolution, and at 18.7 and 36.5 GHz with 5 km spatial resolution. SIC algorithms are based on empirical methods, using the difference in radiometric signatures between the ocean and sea ice. Up to now, the existing algorithms have been limited in the number of channels they use. In this study, we proposed a new SIC algorithm called Ice Concentration REtrieval from the Analysis of Microwaves (IceCREAM). It can accommodate a large range of channels, and it is based on the optimal estimation. Linear relationships between the satellite measurements and the SIC are derived from the Round Robin Data Package of the sea ice Climate Change Initiative. The 6 and 10 GHz channels are very sensitive to the sea ice presence, whereas the 18 and 36 GHz channels have a better spatial resolution. A data fusion method is proposed to combine these two estimations. Therefore, IceCREAM will provide SIC estimates with the good accuracy of the 6+10GHz combination, and the high spatial resolution of the 18+36GHz combination.

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

MAUSAM ◽  
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.  

scholarly journals Ground-based observations of cloud and drizzle liquid water path in stratocumulus clouds

2020 ◽  
Vol 13 (3) ◽  
pp. 1485-1499 ◽  
Author(s):  
Maria P. Cadeddu ◽  
Virendra P. Ghate ◽  
Mario Mech
Keyword(s):  
Liquid Water ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Cloud Base ◽  
Radiative Cooling ◽  
Liquid Water Path ◽  
Cell Systems ◽  
Water Path ◽  
Closed Cell ◽  
Stratocumulus Clouds

Abstract. The partition of cloud and drizzle water path in precipitating clouds plays a key role in determining the cloud lifetime and its evolution. A technique to quantify cloud and drizzle water path by combining measurements from a three-channel microwave radiometer (23.8, 30, and 90 GHz) with those from a vertically pointing Doppler cloud radar and a ceilometer is presented. The technique is showcased using 1 d of observations to derive precipitable water vapor, liquid water path, cloud water path, drizzle water path below the cloud base, and drizzle water path above the cloud base in precipitating stratocumulus clouds. The resulting cloud and drizzle water path within the cloud are in good qualitative agreement with the information extracted from the radar Doppler spectra. The technique is then applied to 10 d each of precipitating closed and open cellular marine stratocumuli. In the closed-cell systems only ∼20 % of the available drizzle in the cloud falls below the cloud base, compared to ∼40 % in the open-cell systems. In closed-cell systems precipitation is associated with radiative cooling at the cloud top <-100Wm-2 and a liquid water path >200 g m−2. However, drizzle in the cloud begins to exist at weak radiative cooling and liquid water path >∼150 g m−2. Our results collectively demonstrate that neglecting scattering effects for frequencies at and above 90 GHz leads to overestimation of the total liquid water path of about 10 %–15 %, while their inclusion paves the path for retrieving drizzle properties within the cloud.

Overview and Applications of the New York State Mesonet Profiler Network

2021 ◽  
Author(s):  
Bhupal Shrestha ◽  
J. A. Brotzge ◽  
J. Wang ◽  
N. Bain ◽  
C. D. Thorncroft ◽  
...  
Keyword(s):  
New York ◽  
Situational Awareness ◽  
Microwave Radiometer ◽  
New York State ◽  
Atmospheric Temperature ◽  
Land Breeze ◽  
Doppler Lidar ◽  
Essential Information ◽  
York State ◽  
Wildfire Smoke

AbstractVertical profiles of atmospheric temperature, moisture, wind, and aerosols are essential information for weather monitoring and prediction. Their availability, however, is limited in space and time due to the significant resources required to observe them. To fill this gap, the New York State Mesonet (NYSM) Profiler Network has been deployed as a national testbed to facilitate the research, development and evaluation of ground-based profiling technologies and applications. The testbed comprises 17 profiler stations across the state, forming a long-term regional observational network. Each Profiler station is comprised of a ground-based Doppler lidar, a microwave radiometer (MWR) and an environmental Sky Imaging Radiometer (eSIR). Thermodynamic profiles (temperature and humidity) from the MWR; wind and aerosol profiles from the Doppler lidar; and solar radiance and optical depth parameters from the eSIR are collected, processed, disseminated, and archived every 10 minutes. This paper introduces the NYSM Profiler Network and reviews the network design and siting, instrumentation, network operations and maintenance, data and products, and some example applications highlighting the benefits of the network. Some sample applications include improved situational awareness and monitoring of the sea/land breeze, long-range wildfire smoke transport, air quality (PM2.5 and AOD) and boundary layer height. Ground-based profiling systems promise a path forward for filling a critical gap in the nation’s observing system with the potential to improve analysis and prediction for many weather-sensitive sectors, such as aviation, ground transportation, health, and wind energy.

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