scholarly journals Sensitivity of aerosol and cloud effects on radiation to cloud types: comparison between deep convective clouds and warm stratiform clouds over one-day period

2009 ◽  
Vol 9 (7) ◽  
pp. 2555-2575 ◽  
Author(s):  
S. S. Lee ◽  
L. J. Donner ◽  
V. T. J. Phillips
Keyword(s):  
Mesoscale Convective System ◽  
Convective System ◽  
Ice Clouds ◽  
Cloud Forcing ◽  
Convective Clouds ◽  
Lower Cloud ◽  
Stratiform Clouds ◽  
Stratocumulus Clouds ◽  
Mesoscale Convective ◽  
Aerosol Effects

Abstract. Cloud and aerosol effects on radiation in two contrasting cloud types, a deep mesoscale convective system (MCS) and warm stratocumulus clouds, are simulated and compared. At the top of the atmosphere, 45–81% of shortwave cloud forcing (SCF) is offset by longwave cloud forcing (LCF) in the MCS, whereas warm stratiform clouds show the offset of less than ~20%. 28% of increased negative SCF is offset by increased LCF with increasing aerosols in the MCS at the top of the atmosphere. However, the stratiform clouds show the offset of just around 2–5%. Ice clouds as well as liquid clouds play an important role in the larger offset in the MCS. Lower cloud-top height and cloud depth, characterizing cloud types, lead to the smaller offset of SCF by LCF and the offset of increased negative SCF by increased LCF at high aerosol in stratocumulus clouds than in the MCS. Supplementary simulations show that this dependence of modulation of LCF on cloud depth and cloud-top height is also simulated among different types of convective clouds.

scholarly journals Cloud and aerosol effects on radiation in deep convective clouds: comparison with warm stratiform clouds

2008 ◽  
Vol 8 (4) ◽  
pp. 15291-15341
Author(s):  
S. S. Lee ◽  
L. J. Donner ◽  
V. T. J. Phillips
Keyword(s):  
Longwave Radiation ◽  
Ice Clouds ◽  
Cloud Forcing ◽  
Convective Clouds ◽  
Lower Cloud ◽  
Deep Convective Clouds ◽  
Stratiform Clouds ◽  
Stratocumulus Clouds ◽  
Shallow Clouds ◽  
Aerosol Effects

Abstract. Cloud and aerosol effects on radiation in two contrasting cloud types, a deep convective mesoscale cloud ensemble (MCE) and warm stratocumulus clouds, are simulated and compared. At the top of the atmosphere, 45–81% of shortwave cloud forcing (SCF) is offset by longwave cloud forcing (LCF) in the MCE, whereas warm stratiform clouds show the offset of less than ~20%. 28% of increased negative SCF is offset by increased LCF with increasing aerosols in the MCE at the top of the atmosphere. However, the stratiform clouds show the offset of just around 2–5%. Ice clouds as well as liquid clouds play an important role in the larger offset in the MCE. Hence, this study indicates effects of deep convective clouds on radiation and responses of deep convective clouds to aerosols are quite different from those of shallow clouds through the different modulation of longwave radiation; the presence of ice clouds in deep convective clouds contributes to the different modulation of longwave radiation significantly. Different cloud types, characterized by cloud depth and cloud-top height, play critical roles in those different modulations of LCF between the MCE and stratocumulus clouds. Lower cloud-top height and cloud depth lead to smaller offset of SCF by LCF and offset of increased negative SCF by increased LCF at high aerosol in stratocumulus clouds than in the MCE. Supplementary simulations show this dependence of modulation of LCF on cloud depth and cloud-top height is not limited to those two contrasting cloud types. The dependence is also simulated among different types of convective clouds, indicating the assessment of effects of varying cloud types on radiation due to climate changes can be critical to better prediction of climate.

scholarly journals Effect of Aerosol on Circulations and Precipitation in Deep Convective Clouds

2012 ◽  
Vol 69 (6) ◽  
pp. 1957-1974 ◽  
Author(s):  
Seoung Soo Lee
Keyword(s):  
Mesoscale Convective System ◽  
Cloud System ◽  
Convective System ◽  
Entire Domain ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Mesoscale Convective

Abstract This study examines the effect of a mesoscale perturbation of aerosol on a larger-scale cloud system driven by deep convective clouds. An aerosol-perturbed domain of size 120 km is prescribed in the middle of the larger-scale domain of size 1100 km. Aerosol perturbations in the mesoscale domain result in an intensification of convection in a mesoscale convective system (MCS). This leads to an intensification of the larger-scale circulations, which in turn leads to an intensification of the larger-scale subsidence. While the invigorated convection enhances precipitation in the MCS, the intensified larger-scale subsidence acts to increase the larger-scale stability and thus to suppress convection and precipitation in the larger-scale domain. The suppression of precipitation in the larger-scale domain outweighs the enhancement of precipitation in the mesoscale domain, leading to suppressed precipitation over the entire domain. The ramifications of aerosol perturbations therefore need to be considered on scales much larger than the scale of the perturbation.

Ensemble Probabilistic Prediction of a Mesoscale Convective System and Associated Polarimetric Radar Variables Using Single-Moment and Double-Moment Microphysics Schemes and EnKF Radar Data Assimilation

2017 ◽  
Vol 145 (6) ◽  
pp. 2257-2279 ◽  
Author(s):  
Bryan J. Putnam ◽  
Ming Xue ◽  
Youngsun Jung ◽  
Nathan A. Snook ◽  
Guifu Zhang
Keyword(s):  
Mesoscale Convective System ◽  
Radar Data ◽  
Convective Precipitation ◽  
Convective System ◽  
Ensemble Forecasts ◽  
Verification Methods ◽  
Probabilistic Forecasts ◽  
Mesoscale Convective ◽  
Single Moment ◽  
Double Moment

Abstract Ensemble-based probabilistic forecasts are performed for a mesoscale convective system (MCS) that occurred over Oklahoma on 8–9 May 2007, initialized from ensemble Kalman filter analyses using multinetwork radar data and different microphysics schemes. Two experiments are conducted, using either a single-moment or double-moment microphysics scheme during the 1-h-long assimilation period and in subsequent 3-h ensemble forecasts. Qualitative and quantitative verifications are performed on the ensemble forecasts, including probabilistic skill scores. The predicted dual-polarization (dual-pol) radar variables and their probabilistic forecasts are also evaluated against available dual-pol radar observations, and discussed in relation to predicted microphysical states and structures. Evaluation of predicted reflectivity (Z) fields shows that the double-moment ensemble predicts the precipitation coverage of the leading convective line and stratiform precipitation regions of the MCS with higher probabilities throughout the forecast period compared to the single-moment ensemble. In terms of the simulated differential reflectivity (ZDR) and specific differential phase (KDP) fields, the double-moment ensemble compares more realistically to the observations and better distinguishes the stratiform and convective precipitation regions. The ZDR from individual ensemble members indicates better raindrop size sorting along the leading convective line in the double-moment ensemble. Various commonly used ensemble forecast verification methods are examined for the prediction of dual-pol variables. The results demonstrate the challenges associated with verifying predicted dual-pol fields that can vary significantly in value over small distances. Several microphysics biases are noted with the help of simulated dual-pol variables, such as substantial overprediction of KDP values in the single-moment ensemble.

scholarly journals Comprehensive Analysis of a Coast Thunderstorm That Produced a Sprite over the Bohai Sea

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 718
Author(s):  
Cong Pan ◽  
Jing Yang ◽  
Kun Liu ◽  
Yu Wang
Keyword(s):  
Bohai Sea ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Return Stroke ◽  
Absolute Value ◽  
Transient Luminous Events ◽  
Stratiform Region ◽  
Before And After ◽  
Mesoscale Convective ◽  
Cloud To Ground Lightning

Sprites are transient luminous events (TLEs) that occur over thunderstorm clouds that represent the direct coupling relationship between the troposphere and the upper atmosphere. We report the evolution of a mesoscale convective system (MCS) that produced only one sprite event, and the characteristics of this thunderstorm and the related lightning activity are analyzed in detail. The results show that the parent flash of the sprite was positive cloud-to-ground lightning (+CG) with a single return stroke, which was located in the trailing stratiform region of the MCS with a radar reflectivity of 25 to 35 dBZ. The absolute value of the negative CG (−CG) peak current for half an hour before and after the occurrence of the sprite was less than 50 kA, which was not enough to produce the sprite. Sprites tend to be produced early in the maturity-to-dissipation stage of the MCS, with an increasing percentage of +CG to total CG (POP), indicating that the sprite production was the attenuation of the thunderstorm and the area of the stratiform region.

scholarly journals Evaluating Smartphone Pressure Observations for Mesoscale Analyses and Forecasts

2017 ◽  
Vol 32 (2) ◽  
pp. 511-531 ◽  
Author(s):  
Luke E. Madaus ◽  
Clifford F. Mass
Keyword(s):  
United States ◽  
Rural Areas ◽  
Mesoscale Convective System ◽  
Convective System ◽  
Active Period ◽  
Eastern United States ◽  
Short Term ◽  
Mesoscale Convective ◽  
Dynamic Structures ◽  
Further Development

Abstract Smartphone pressure observations have the potential to greatly increase surface observation density on convection-resolving scales. Currently available smartphone pressure observations are tested through assimilation in a mesoscale ensemble for a 3-day, convectively active period in the eastern United States. Both raw pressure (altimeter) observations and 1-h pressure (altimeter) tendency observations are considered. The available observation density closely follows population density, but observations are also available in rural areas. The smartphone observations are found to contain significant noise, which can limit their effectiveness. The assimilated smartphone observations contribute to small improvements in 1-h forecasts of surface pressure and 10-m wind, but produce larger errors in 2-m temperature forecasts. Short-term (0–4 h) precipitation forecasts are improved when smartphone pressure and pressure tendency observations are assimilated as compared with an ensemble that assimilates no observations. However, these improvements are limited to broad, mesoscale features with minimal skill provided at convective scales using the current smartphone observation density. A specific mesoscale convective system (MCS) is examined in detail, and smartphone pressure observations captured the expected dynamic structures associated with this feature. Possibilities for further development of smartphone observations are discussed.

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