scholarly journals Low cloud precipitation climatology in the southeastern Pacific marine stratocumulus region using CloudSat

2013 ◽  
Vol 8 (1) ◽  
pp. 014027 ◽  
Author(s):  
Anita D Rapp ◽  
Matthew Lebsock ◽  
Tristan L’Ecuyer
Keyword(s):  
Marine Stratocumulus ◽  
Precipitation Climatology ◽  
Southeastern Pacific ◽  
Low Cloud

scholarly journals Meteorological and Aerosol Effects on Marine Stratocumulus

2016 ◽  
Vol 73 (2) ◽  
pp. 807-820 ◽  
Author(s):  
Zhe Li ◽  
Huiwen Xue ◽  
Jen-Ping Chen ◽  
Wei-Chyung Wang
Keyword(s):  
Precipitation Amount ◽  
Wrf Model ◽  
Cloud Fraction ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Marine Stratocumulus ◽  
Diurnal Cycles ◽  
Microphysical Properties ◽  
Southeastern Pacific ◽  
Lower Cloud

Abstract This study investigates the effects of meteorological conditions and aerosols on marine stratocumulus in the southeastern Pacific using the Weather Research and Forecasting (WRF) Model. Two regimes with different temperature and moisture conditions in the finest model domain are investigated. The western regime is around 87°–79°W, while the eastern regime is around 79°–71°W. In both regimes, cloud fraction, liquid water path (LWP), cloud thickness, and precipitation show significant diurnal cycles. Cloud fraction can be 0.83 during the night and down to 0.29 during the day in the western regime. The diurnal cycles in the eastern regime have smaller amplitudes but are still very strong. Stratocumulus properties also differ in the two regimes. Compared to the western regime, the eastern regime has lower temperature, higher relative humidity, and a more coupled boundary layer, leading to higher cloud fraction (by 0.11) and lower cloud-base height. The eastern regime also has lower inversion height that causes lower cloud-top height and thinner clouds and, hence, lower LWP and less precipitation. Cloud microphysical properties are very sensitive to aerosols in both regimes. Increasing aerosols greatly increase cloud number concentration, decrease cloud effective radius, and suppress precipitation. Cloud macrophysical properties (cloud fraction, LWP) are not sensitive to aerosols in either regime, most notably in the eastern regime where precipitation amount is less. The changes in cloud fraction and LWP caused by changes in aerosol concentrations are smaller than the changes in the diurnal cycle and the spatial variability between the two regimes.

scholarly journals Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem

2011 ◽  
Vol 11 (8) ◽  
pp. 22663-22718 ◽  
Author(s):  
Q. Yang ◽  
J. D. Fast ◽  
H. Wang ◽  
R. C. Easter ◽  
H. Morrison ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Cloud Base ◽  
Model Assessment ◽  
Microphysics Scheme ◽  
Marine Stratocumulus ◽  
Aerosol Cloud ◽  
Southeastern Pacific ◽  
Temperature And Humidity ◽  
Stratocumulus Clouds ◽  
Aerosol Cloud Interactions

Abstract. In the recent chemistry version (v3.3) of the Weather Research and Forecasting (WRF-Chem) model, we have coupled the Morrison double-moment microphysics scheme with interactive aerosols so that two-way aerosol-cloud interactions are included in the simulations. We have used this new WRF-Chem functionality in a study focused on assessing predictions of aerosols, marine stratocumulus clouds, and their interactions over the Southeast Pacific using measurements from the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) and satellite retrievals. This study also serves as a detailed analysis of our WRF-Chem simulations contributed to the VOCALS model Assessment (VOCA) project. The WRF-Chem 31-day (15 October–16 November 2008) simulation with aerosol-cloud interactions (AERO hereafter) is also compared to a simulation (MET hereafter) with fixed cloud droplet number concentrations assumed by the default in Morrison microphysics scheme with no interactive aerosols. The well-predicted aerosol properties such as number, mass composition, and optical depth lead to significant improvements in many features of the simulated stratocumulus clouds: cloud optical properties and microphysical properties such as cloud top effective radius, cloud water path, and cloud optical thickness, and cloud macrostructure such as cloud depth and cloud base height. In addition to accounting for the aerosol direct and semi-direct effects, these improvements feed back to the prediction of boundary-layer characteristics and energy budgets. Particularly, inclusion of interactive aerosols in AERO strengthens the temperature and humidity gradients within the capping inversion layer and lowers the marine boundary layer depth by 150 m from that of the MET simulation. Mean top-of-the-atmosphere outgoing shortwave fluxes, surface latent heat, and surface downwelling longwave fluxes are in better agreement with observations in AERO, compared to the MET simulation. Nevertheless, biases in some of the simulated meteorological quantities (e.g., MBL temperature and humidity over the remote ocean) and aerosol quantities (e.g., overestimations of supermicron sea salt mass) might affect simulated stratocumulus and energy fluxes over the southeastern Pacific Ocean, and require further investigations. Although not perfect, the overall performance of the regional model in simulating mesoscale aerosol-cloud interactions is encouraging and suggests that the inclusion of spatially varying aerosol characteristics is important when simulating marine stratocumulus over the southeastern Pacific.

scholarly journals Identifying meteorological influences on marine low cloud mesoscale morphology using deep learning classifications

2020 ◽  
Author(s):  
Johannes Mohrmann ◽  
Robert Wood ◽  
Tianle Yuan ◽  
Hua Song ◽  
Ryan Eastman ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Layer Structure ◽  
Surface Wind ◽  
Cloud Properties ◽  
Southeastern Pacific ◽  
Distribution Boundary ◽  
Mesoscale Convective ◽  
Low Cloud ◽  
Meteorological Influences

Abstract. Marine low cloud mesoscale morphology in the southeastern Pacific Ocean is analyzed using a large dataset of machine-learning generated classifications spanning three years. Meteorological variables and cloud properties are composited by mesoscale cloud type, showing distinct meteorological regimes of marine low cloud organization from the tropics to the midlatitudes. The presentation of mesoscale cellular convection, with respect to geographic distribution, boundary layer structure, and large-scale environmental conditions, agrees with prior knowledge. Two tropical and subtropical cumuliform boundary layer regimes, suppressed cumulus and clustered cumulus, are studied in detail. The patterns in precipitation, circulation, column water vapor, and cloudiness are consistent with the representation of marine shallow mesoscale convective self-aggregation by large eddy simulations of the boundary layer. Although they occur under similar large-scale conditions, the suppressed and clustered low cloud types are found to be well-separated by variables associated with low-level mesoscale circulation, with surface wind divergence being the clearest discriminator between them, whether reanalysis or satellite observations are used. Clustered regimes are associated with surface convergence and suppressed regimes are associated with surface divergence.

scholarly journals Applying deep learning to NASA MODIS data to create a community record of marine low-cloud mesoscale morphology

2020 ◽  
Vol 13 (12) ◽  
pp. 6989-6997
Author(s):  
Tianle Yuan ◽  
Hua Song ◽  
Robert Wood ◽  
Johannes Mohrmann ◽  
Kerry Meyer ◽  
...  
Keyword(s):  
Cumulus Convection ◽  
Training Set ◽  
Average Precision ◽  
Team Members ◽  
Southeastern Pacific ◽  
Low Clouds ◽  
Low Cloud ◽  
One Step ◽  
Observational Record ◽  
Cross Type

Abstract. Marine low clouds display rich mesoscale morphological types and distinct spatial patterns of cloud fields. Being able to differentiate low-cloud morphology offers a tool for the research community to go one step beyond bulk cloud statistics such as cloud fraction and advance the understanding of low clouds. Here we report the progress of our project that aims to create an observational record of low-cloud mesoscale morphology at a near-global (60∘ S–60∘ N) scale. First, a training set is created by our team members manually labeling thousands of mesoscale (128×128) MODIS scenes into six different categories: stratus, closed cellular convection, disorganized convection, open cellular convection, clustered cumulus convection, and suppressed cumulus convection. Then we train a deep convolutional neural network model using this training set to classify individual MODIS scenes at 128×128 resolution and test it on a test set. The trained model achieves a cross-type average precision of about 93 %. We apply the trained model to 16 years of data over the southeastern Pacific. The resulting climatological distribution of low-cloud morphology types shows both expected and unexpected features and suggests promising potential for low-cloud studies as a data product.

scholarly journals Identifying meteorological influences on marine low-cloud mesoscale morphology using satellite classifications

2021 ◽  
Vol 21 (12) ◽  
pp. 9629-9642
Author(s):  
Johannes Mohrmann ◽  
Robert Wood ◽  
Tianle Yuan ◽  
Hua Song ◽  
Ryan Eastman ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Layer Structure ◽  
Surface Wind ◽  
Cloud Properties ◽  
Southeastern Pacific ◽  
Distribution Boundary ◽  
Mesoscale Convective ◽  
Low Cloud ◽  
Meteorological Influences

Abstract. Marine low-cloud mesoscale morphology in the southeastern Pacific Ocean is analyzed using a large dataset of classifications spanning 3 years generated by machine learning methods. Meteorological variables and cloud properties are composited by the mesoscale cloud type of the classification, showing distinct meteorological regimes of marine low-cloud organization from the tropics to the midlatitudes. The presentation of mesoscale cellular convection, with respect to geographic distribution, boundary layer structure, and large-scale environmental conditions, agrees with prior knowledge. Two tropical and subtropical cumuliform boundary layer regimes, suppressed cumulus and clustered cumulus, are studied in detail. The patterns in precipitation, circulation, column water vapor, and cloudiness are consistent with the representation of marine shallow mesoscale convective self-aggregation by large eddy simulations of the boundary layer. Although they occur under similar large-scale conditions, the suppressed and clustered low-cloud types are found to be well separated by variables associated with low-level mesoscale circulation, with surface wind divergence being the clearest discriminator between them, regardless of whether reanalysis or satellite observations are used. Clustered regimes are associated with surface convergence, while suppressed regimes are associated with surface divergence.

Abrupt cloud clearing of marine stratocumulus in the subtropical southeast Atlantic

Science ◽  
2018 ◽  
Vol 361 (6403) ◽  
pp. 697-701 ◽  
Author(s):  
Sandra E. Yuter ◽  
John D. Hader ◽  
Matthew A. Miller ◽  
David B. Mechem
Keyword(s):  
Gravity Waves ◽  
Global Radiation ◽  
Small Scale ◽  
Radiation Balance ◽  
Mean Flow ◽  
Marine Stratocumulus ◽  
Annual Peak ◽  
Low Cloud ◽  
The Mean ◽  
Atmospheric Gravity

We document rapid and abrupt clearings of large portions of the subtropical marine low cloud deck that have implications for the global radiation balance and climate sensitivity. Over the southeast Atlantic, large areas of stratocumulus are quickly eroded, yielding partial or complete clearing along sharp transitions hundreds to thousands of kilometers in length that move westward at 8 to 12 meters per second and travel as far as 1000+ kilometers from the African coast. The westward-moving cloudiness reductions have an annual peak in occurrence in the period from April through June. The cloud erosion boundaries reduce cloud at ≈10-kilometer scale in less than 15 minutes, move approximately perpendicular to the mean flow, and are often accompanied by small-scale wave features. Observations suggest that the cloud erosion is caused by atmospheric gravity waves.

scholarly journals Patterns of Diurnal Marine Stratocumulus Cloud Fraction Variability

2015 ◽  
Vol 54 (4) ◽  
pp. 847-866 ◽  
Author(s):  
Casey D. Burleyson ◽  
Sandra E. Yuter
Keyword(s):  
Diurnal Cycle ◽  
Cloud Fraction ◽  
High Temporal Resolution ◽  
Marine Stratocumulus ◽  
Radiative Fluxes ◽  
Diurnal Cycles ◽  
Maximum Value ◽  
Low Cloud ◽  
Ne Pacific ◽  
Infrared Data

AbstractThe spatial patterns of subtropical marine stratocumulus cloud fraction variability on diurnal time scales are examined using high-temporal-resolution cloud masks that are based on 30-min, 4 km × 4 km geosynchronous infrared data for 2003–10. This dataset permits comparison of the characteristics of variability in low cloud fraction among the three subtropical marine stratocumulus regions in the northeastern (NE) Pacific, southeastern (SE) Pacific, and SE Atlantic Oceans. In all three regions, the largest diurnal cycles and earliest time of cloud breakup occur on the edges of the cloud field where cloud fractions are generally lower. The rate at which the cloud breaks up during the day is tied to the starting cloud fraction at dawn, which determines the amount of longwave cooling that is initially available to offset shortwave radiative fluxes during the day. The maximum rate of cloud breakup occurs near 1200 LT. Cloud fraction begins to increase by 1600 LT (before the sun sets) and reaches its maximum value just before dawn. The diurnal-cycle characteristics of the SE Pacific and SE Atlantic marine stratocumulus cloud decks are more similar to each other than to those in the NE Pacific. The NE Pacific cloud deck has a smaller-amplitude diurnal cycle, slower rates of cloud breakup during the day for a given cloud fraction at dawn, and a higher probability of cloud breakup overnight.

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