Low-latitude boundary layer clouds as seen by CALIPSO

The distribution of low-level cloud in the tropical belt is investigated using 6 months of Level 2 retrievals from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) at 333 m and 1 km horizontal resolutions. Regional patterns of tropical clouds emerge from the data, matching expectations from existing observations. The advantage of the lidar is highlighted by the distribution of cloud-top height, revealing the preponderance of low-level clouds over the tropical oceans. Over land, cloud top is more uniformly distributed under the influence of diurnal variation. The integrated cloud-top distribution suggests tropical, marine low-cloud amount around 25-30%; a merged CALIPSO-CloudSat product has a similar cloud-top distribution and includes a complementary estimate of cloud fraction based on the lidar detections. The low-cloud distribution is similar to that found in fields of shallow cumulus observed during the Rain in Cumulus Over the Ocean (RICO) field study. The similarity is enhanced by sampling near the RICO site or sampling large-scale conditions similar to those during RICO. This finding shows how satellite observations can help to generalize findings from detailed field observations

Clouds at Barbados are representative of clouds across the trade wind regions in observations and climate models

Trade wind regions cover most of the tropical oceans, and the prevailing cloud type is shallow cumulus. These small clouds are parameterized by climate models, and changes in their radiative effects strongly and directly contribute to the spread in estimates of climate sensitivity. This study investigates the structure and variability of these clouds in observations and climate models. The study builds upon recent detailed model evaluations using observations from the island of Barbados. Using a dynamical regimes framework, satellite and reanalysis products are used to compare the Barbados region and the broader tropics. It is shown that clouds in the Barbados region are similar to those across the trade wind regions, implying that observational findings from the Barbados Cloud Observatory are relevant to clouds across the tropics. The same methods are applied to climate models to evaluate the simulated clouds. The models generally capture the cloud radiative effect, but underestimate cloud cover and show an array of cloud vertical structures. Some models show strong biases in the environment of the Barbados region in summer, weakening the connection between the regional biases and those across the tropics. Even bearing that limitation in mind, it is shown that covariations of cloud and environmental properties in the models are inconsistent with observations. The models tend to misrepresent sensitivity to moisture variations and inversion characteristics. These model errors are likely connected to cloud feedback in climate projections, and highlight the importance of the representation of shallow cumulus convection

The role of precipitation and spatial organization in the response of trade-wind clouds to warming

Using highly resolved large-eddy simulations on two different domain sizes, we investigate the influence of precipitation and spatial organization on the thermodynamic structure of the trade-wind layer, under a uniform 4K warming at constant relative humidity. In non-precipitating simulations the increased surface latent heat flux in the warmer climate produces a deeper and drier cloud layer with reduced cloud fractions between 1.5 and 4km. Precipitation prevents the deepening and drying of the cloud layer in response to warming. Cloud fractions still decrease in the upper cloud layer, because stratiform outflow layers near cloud tops are less pronounced and because the larger liquid water contents are confined to narrower updrafts. Simulations on a sixteen-fold larger domain lead to the spatial organization of clouds into larger and deeper cloud clusters. The presence of deeper clouds results in a shallower, warmer and drier trade-wind layer, with strongly reduced cloud cover. The warming response in the precipitating large-domain simulation nevertheless remains similar to the small-domain precipitating simulation. On the large domain, deeper clouds can also develop without precipitation, because moisture-convection feedbacks strengthen in the absence of cold-pool dynamics. Overall, total cloud cover and albedo decrease only slightly with warming in all cases. This demonstrates the robustness of shallow cumuli—in particular of cloud fraction near the lifting condensation level—to changes in the large-scale environment. This article is protected by copyright. All rights reserved

The environment of precipitating shallow cumulus convection

Quantitative estimates of precipitation in a typical undisturbed trade wind region are derived from 2 months of radar reflectivity data and compared to the meteorological environment determined from soundings, surface flux, and airborne-lidar data. Shallow precipitation was ubiquitous, covering on average about 2% of the region and contributing to at least half of the total precipitation. Echo fractions on the scale of the radar domain range between 0% and 10% and vary greatly within a period from a few hours to a day. Variability in precipitation relates most strongly to variability in humidity and the zonal wind speed, although greater inversion heights and deeper clouds are also evident at times of more rain. The analysis herein suggests that subtle fluctuations in both the strength of the easterlies and in subsidence play a major role in regulating humidity and hence precipitation, even within a given meteorological regime (here, the undisturbed trades). [References: 45

Observations of the variability of shallow trade wind cumulus cloudiness and mass flux

Two years of ground-based remote sensing observations are used to study the vertical structure of marine cumulus near the island of Barbados, including their cloud fraction and mass flux profile. Daily radar derived cloud fraction profiles peak at different height levels depending on the depth of the cumuli and thus the extent to which they precipitate. Nonprecipitating cumuli have a peak cloud fraction of about 5% near mean cloud base (700m), whereas precipitating cumuli tend to have a peak of only 2% near cloud base. Nineteen percent of the precipitating cumuli are accompanied by large cloud fractions near the detrainment level of cumulus tops (similar to 1700m). Day-to-day variations in cloud fraction near cloud base are modest (similar to 3%). Nonprecipitating cumuli have their largest reflectivities near cloud top and an ascending core surrounded by a subsiding shell. Precipitating cumuli with enhanced elevated cloudiness (stratiform outflow) are deeper and contain larger vertical gradients in reflectivity and Doppler velocity than precipitating cumuli without such outflow. Bulk (3h) statistics reveal that nonprecipitating shallow cumuli are active and organized. They contain on average 79% in-cloud updrafts with 86% of them being organized in large coherent structures contributing to a maximum updraft mass flux of 8-36gm(-2)s(-1) just above cloud base. Alternatively, downdrafts contribute insignificantly to the mass flux and show little vertical and temporal variability (0-7gm(-2)s(-1)). Complementary Raman lidar information suggests that updraft mass flux profile slope is inversely related to environmental relative humidity

The Development and Validation of the Group Leader Intervention Scales

The purpose of the study was to develop and validate an instrument for examining therapist interventions in group counseling settings. The Group Leader Intervention Scales (GLIS) is a verbal response mode system designed to code group leader verbalizations on six group process variables (structure, group cohesion, modeling, information, exploration, and feedback), and on eleven subscales that examine various aspects of the main categories. The GLIS was developed though a content analysis of session transcripts from a group intervention for children that used stories and peer group processes to increase social problem-solving. High levels of interrater reliability were established between three raters for the six group process variables, and for nine of the eleven subscales. Initial validity of the new instrument was demonstrated by its ability to distinguish between groups based on treatment response (high or low cognitive treatment response), and based on stage of treatment (early, middle, or late)

Congruence of Self-Other Perceptions about Competence, Peer Victimization, and Bullying as Predictors of Self-Reported Emotions

This study examined self-, teacher-, and peer-perceptions of competence, peer victimization, and bullying behavior as they relate to self-reported depression, anxiety, anger, and global self-worth. Participants included 99 second- and third-grade students and their teachers from one school located in the Washington, DC metropolitan area. The sample of students was ethnically diverse (66.7% African American, 17.2% Hispanic, 11.1% Asian American, 5.1% White). Preliminary analyses were conducted to examine the relationships among self-perceptions. As expected, self-perceptions of competence (social acceptance, behavioral conduct, academic competence) positively correlated with one another, where self-perceived victimization and bullying negatively correlated with self-perceived social acceptance and behavioral conduct. As expected, the aforementioned self-perceptions were significantly related to self-reported emotions. Here, self-perceived victimization uniquely predicted self-reported depression and anxiety scores, self-perceived academic competence uniquely predicted self-reported anger scores, and self-perceived academic competence and behavioral conduct uniquely predicted global self-worth scores. Two sets of hypotheses were tested regarding the congruence of self-, teacher-, and peer-perceptions. First, as predicted, teacher- and peer-perceptions more strongly related with one another than with self-perceptions. Linked to this finding, self-perceived victimization and bullying were more highly predictive of self-reported competence, where teacher- and peer-perceived victimization and bullying were more highly predictive of teacher- and peer-reported competence. Second, the relative impact of self-perceptions and discrepancies between self- and other-perceptions on self-reported emotions was examined. This is a departure from past research, which has typically examined self-other discrepancies independent of self-perceptions. Results showed that self-perceptions were more strongly related to self-reported emotions than were self-other discrepancies. However, interactions between these variables in a subset of the analyses argue for the inclusion of self- and other-perceptions in this line of research. The pattern of interactions suggests that discrepancies between self- and other-perceptions had little impact on self-reported emotions for children who reported low competence or high victimization. These children tended to report more negative emotions compared to peers whether their self-appraisals agreed or disagreed with others' appraisals. Conversely, children who reported high competence or low victimization often reported more negative emotions compared to peers when their appraisals were unfavorable relative to others' appraisals

The representation of the trade winds in ECMWF forecasts and reanalyses during EUREC4A

The characterization of systematic forecast errors in lower-tropospheric winds is an essential component of model improvement. This paper is motivated by a global, long-standing surface bias in the operational medium-range weather forecasts produced with the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). Over the tropical oceans, excessive easterly flow is found. A similar bias is found in the western North Atlantic trades, where the EUREC 4 A field campaign provides an unprecedented wealth of measurements. We analyze the wind bias in the IFS and ERA5 reanalysis throughout the entire lower troposphere during EUREC4 A. The wind bias varies greatly from day to day, resulting in root mean square errors (RMSEs) up to 2.5 m s(-1), with a mean wind speed bias up to -1 m s(-1) near and above the trade inversion in the forecasts and up to -0.5 m s(-1) in reanalyses. These biases are insensitive to the assimilation of sondes. The modeled zonal and meridional winds exhibit a diurnal cycle that is too strong, leading to a weak wind speed bias everywhere up to 5 km during daytime but a wind speed bias below 2 km at nighttime that is too strong. Removing momentum transport by shallow convection reduces the wind bias near the surface but leads to stronger easterly near cloud base. The update in moist physics in the newest IFS cycle (cycle 47r3) reduces the meridional wind bias, especially during daytime. Below 1 km, modeled friction due to unresolved physical processes appears to be too strong but is (partially) compensated for by the dynamics, making this a challenging coupled problem