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An algorithm that derives the nonprecipitating cloud liquid water path Wcld from CloudSat using a surface reference technique (SRT) is presented. The uncertainty characteristics of the SRT are evaluated. It is demonstrated that an accurate analytical formulation for the pixel-scale precision can be derived. The average precision of the SRT is estimated to be 34 g m−2 at the individual pixel scale; however, precision systematically decreases from around 30 to 40 g m−2 as cloud fraction varies from 0% to 100%. The retrievals of clear-sky Wcld have a mean bias of 0.9 g m−2. Output from a large-eddy simulation coupled to a radar simulator shows that an additional bias of −8% may result from nonuniformity within the footprint of cloudy pixels. The retrieval yield for the SRT, measured relative to all warm clouds over ocean between 60°N and 60°S latitude is 43%. The SRT Wcld is compared with one estimate of Wcld from the Moderate Resolution Imaging Spectroradiometer (MODIS) using an adiabatic cloud profile and an effective radius derived from 3.7-μm reflectance. A strong correlation between the mean MODIS Wcld and SRT Wcld is found across diverse cloud regimes, but with biases in the mean Wcld that are cloud-regime dependent. Overall, the mean bias of the SRT relative to MODIS is −13.1 g m−2. Systematic underestimates of Wcld by the SRT resulting from nonuniform beamfilling cannot be ruled out as an explanation for the retrieval bias.

The convective mass flux within tropical convection influences the large-scale circulation, drives cloud radiative forcing, has integral links to the production of fresh water, and impacts extreme weather. CMF forms the focus of the recently selected Investigation of Convective Updrafts (INCUS) mission to be launched in 2026. This NASA mission is comprised of 3 spacecraft, all of which will carry a Ka-band cloud radar. One spacecraft will also carry a passive microwave radiometer. The 3 smallsats are to be separated by time intervals of 30, 90 and 120 seconds, thus allowing for the rapid and systematic sampling of the same storm with all three spacecraft. These time intervals (delta-ts) also facilitate the investigation of the magnitude and evolution of CMF, which will be examined as a function of storm type, storm lifecycle and environmental properties. INCUS will therefore provide the first global systematic investigation into CMF and its evolution within deep tropical convection.A wide range of research tasks have been conducted in preparation for the INCUS mission and the development of the INCUS algorithms including: (1) running and analyzing extensive suites of large-domain, high-resolution model simulations; (2) examining ground-based Doppler radar observations obtained using adaptive scanning techniques during several recent field campaigns; and (3) evaluating anvil characteristics using passive microwave radiometer and geoIR data. This talk will focus on three specific highlights arising from these modeling and observational analyses. First, we will examine the temporal scales of updraft variability. Second, we will analyze the relationship between ice water path cores and convective updrafts. Finally, we will demonstrate proof of the INCUS delta-t concept linking changes in reflectivity to CMF through the use of ground-based radar analyses.

This paper is the first attempt to document a simple convection-tracking method based on the IMERG precipitation product to generate an IMERG-based Convection Tracking (IMERG-CT) dataset. Up to now, precipitation datasets have been Eulerian accumulations. Now with IMERG-CT, we can estimate total rainfall based on Lagrangian accumulations, which is a very important step in diagnosing cloud-precipitation process following the evolution of air masses. Convection-tracking algorithms have traditionally been developed on the basis of brightness temperature (Tb) from satellite infrared (IR) retrievals. However, vigorous rainfall can be produced by warm-topped systems in a moist environment; this situation cannot be captured by traditional IR-based tracking but is observed in IMERG-CT. Therefore, an advantage of IMERG-CT is its ability to include the previously missing information of shallow clouds that grow into convective storms, which provides us more-complete life cycle records of convective storms than traditional IR-based tracking does. This study also demonstrates the utility of IMERG-CT through investigating various properties of convective systems in terms of the evolution before and after peak precipitation rate and amount. For example, composite analysis reveals a link between evolution of precipitation and convective development: the signature of stratiform anvils remaining after the storm has produced the maximum rainfall, as average Tb stays almost constant for 5 h after the peak of precipitation. Our study highlights the importance of joint analysis of cloud and precipitation data in time sequence, which helps to elucidate the underlying dynamic processes producing tropical rainfall and its resultant effects on the atmospheric thermodynamics.

The latest configuration of the Hadley Centre Global Environmental Model version 3 (HadGEM3) contains significant changes in the formulation of warm rain processes and aerosols. We evaluate the impacts of these changes in the simulation of warm rain formation processes using A-Train observations. We introduce a new model evaluation tool, quartile-based Contoured Frequency by Optical Depth Diagrams (CFODDs), in order to fill in some blind spots that conventional CFODDs have. Results indicate that HadGEM3 has weak linkage between the size of particle radius and warm rain formation processes, and switching to the new warm rain microphysics scheme causes more difference in warm rain formation processes than switching to the new aerosol scheme through reducing overly produced drizzle mode in HadGEM3. Finally, we run an experiment in which we perturb the second aerosol indirect effect (AIE) to study the rainfall-aerosol interaction in HadGEM3. Since the large changes in the cloud droplet number concentration (CDNC) appear in the AIE experiment, a large impact in warm rain diagnostics is expected. However, regions with large fractional changes in CDNC show a muted change in precipitation, arguably because large-scale constraints act to reduce the impact of such a big change in CDNC. The adjustment in cloud liquid water path to the AIE perturbation produces a large negative shortwave forcing in the midlatitudes.

A review of the progression of cloud physics from a subdiscipline of meteorology into the global science it is today is described. The discussion briefly touches on the important post‐war contributions of three key individuals who were instrumental in developing cloud physics into a global science. These contributions came on the heels of the post‐war weather modification efforts that influenced much of the early development of cloud physics. The review is centred on the properties of warm clouds primarily to limit the scope of the article and the connection between the early contributions to cloud physics and the current vexing problem of aerosol effects on cloud albedo is underlined. Progress toward estimating cloud properties from space and insights on warm cloud processes are described. Measurements of selected cloud properties, such as cloud liquid water path are now mature enough that multi‐decadal time series of these properties exist and this climatology is used to compare to analogous low‐cloud properties taken from global climate models. The too‐wet (and thus too bright) and the too‐dreary biases of models are called out underscoring the challenges we still face in representing warm clouds in Earth system models. We also provide strategies for using observations to constrain the indirect radiative forcing of the climate system.

We use the Atmospheric Infrared Sounder (AIRS) version 6 ice cloud property and thermodynamic phase retrievals to quantify variability and 14-year trends in ice cloud frequency, ice cloud top temperature (Tci), ice optical thickness (τi) and ice effective radius (rei). The trends in ice cloud properties are shown to be independent of trends in information content and χ2. Statistically significant decreases in ice frequency, τi, and ice water path (IWP) are found in the SH and NH extratropics, but trends are of much smaller magnitude and statistically insignificant in the tropics. However, statistically significant increases in rei are found in all three latitude bands. Perturbation experiments consistent with estimates of AIRS radiometric stability fall significantly short of explaining the observed trends in ice properties, averaging kernels, and χ2 trends. Values of rei are larger at the tops of opaque clouds and exhibit dependence on surface wind speed, column water vapour (CWV) and surface temperature (Tsfc) with changes up to 4–5 µm but are only 1.9 % of all ice clouds. Non-opaque clouds exhibit a much smaller change in rei with respect to CWV and Tsfc. Comparisons between DARDAR and AIRS suggest that rei is smallest for single-layer cirrus, larger for cirrus above weak convection, and largest for cirrus above strong convection at the same cloud top temperature. This behaviour is consistent with enhanced particle growth from radiative cooling above convection or large particle lofting from strong convection.

A common problem in climate models is that they are likely to produce rain at a faster rate than is observed and therefore produce too much light rain (e.g., drizzle). Interestingly, the Pacific Northwest National Laboratory (PNNL) multiscale modeling framework (MMF), whose warm-rain formation process is more realistic than other global models, has the opposite problem: the rain formation process in PNNL-MMF is less efficient than the real world. To better understand the microphysical processes in warm cloud, this study documents the model biases in PNNL-MMF and evaluates warm cloud properties, subgrid variability, and microphysics, using A-Train satellite observations to identify sources of model biases in PNNL-MMF. Like other models PNNL-MMF underpredicts the warm cloud fraction with compensating large optical depths. Associated with these compensating errors in cloudiness are compensating errors in the precipitation process. For a given liquid water path, clouds in the PNNL-MMF are less likely to produce rain than are real-world clouds. However, when the model does produce rain it is able to produce stronger precipitation than reality. As a result PNNL-MMF produces about the correct mean rain rate with an incorrect distribution of rates. The subgrid variability in PNNL-MMF is also tested, and results are fairly consistent with observations, suggesting that the possible sources of model biases are likely to be due to errors in its microphysics or dynamics rather than errors in the subgrid-scale variability produced by the embedded cloud resolving model.

Although Tropical Rainfall Measuring Mission (TRMM) and CloudSat/CALIPSO fly in different orbits, they frequently cross each other so that for the period between 2006 and 2010, a total of 15,986 intersect lines occurred within 20 min of each other from 30°S to 30°N, providing a rare opportunity to study tropical cloud and precipitation regimes and their internal vertical structure from near-simultaneous measurements by these active sensors. A k-means cluster analysis of TRMM and CloudSat matchups identifies three tropical cloud and precipitation regimes: the first two regimes correspond to, respectively, organized deep convection with heavy rain and cirrus anvils with moderate rain; the third regime is a convectively suppressed regime that can be further divided into three subregimes, which correspond to, respectively, stratocumulus clouds with drizzle, cirrus overlying low clouds, and nonprecipitating cumulus. Inclusion of CALIPSO data adds to the dynamic range of cloud properties and identifies one more cluster; subcluster analysis further identifies a thin, midlevel cloud regime associated with tropical mountain ranges. The radar-lidar cloud regimes are compared with the International Satellite Cloud Climatology Project (ISCCP) weather states (WSs) for the extended tropics. Focus is placed on the four convectively active WSs, namely, WS1–WS4. ISCCP WS1 and WS2 are found to be counterparts of Regime 1 and Regime 2 in radar-lidar observations, respectively. ISCCP WS3 and WS4, which are mainly isolated convection and broken, detached cirrus, do not have a strong association with any individual radar and lidar regimes, a likely effect of the different sampling strategies between ISCCP and active sensors and patchy cloudiness of these WSs.

A previous study explored land–ocean differences in the warm-rain formation process. In that study, aerosol effects were removed, or at least partially removed, but some land–ocean differences remained. Therefore, the study hypothesized that the land–ocean difference in the microphysical structure of warm clouds and in the formation of warm rain can be explained by differences in the nature of updraughts. To test this hypothesis, this study provides a detailed analysis of the land–ocean differences in warm clouds using a combination of CloudSat and MODerate-resolution Imaging Spectroradiometer (MODIS) observations, ground-based measurements obtained from Atmospheric Radiation Measurement (ARM), as well as a simple model framework. Our results show that a stronger updraught increases the height at which significant coalescence begins, and also prolongs the lifetime of falling drops promoting larger droplet growth. A consequence of this difference is that drizzle is less frequently observed at cloud base over land. Our results point to the critical role of the strength of the convective updraught in the warm-rain formation process.

This paper is the follow on to a previous publication by the authors, which investigated the relationship between the level of neutral buoyancy (LNB) determined from the ambient sounding and the actual outflow levels using mainly CloudSat observations. The goal of the current study is to provide a more complete characterization of LNB, deep convective outflow, and convective core, and the relationship among them, as well as the dependence on environmental parameters and convective system size. A proxy is introduced to estimate convective entrainment, namely, the difference between the LNB (based on the ambient sounding) and the actual outflow height. The principal findings are as follows: (1) Deep convection over the Warm Pool has larger entrainment rates and smaller convective cores than the counterpart over the two tropical land regions (Africa and Amazonia), lending observational support to a long-standing assumption in convection models concerning the negative relationship between the two parameters. (2) The differences in internal vertical structure of convection between the two tropical land regions and the Warm Pool suggest that deep convection over the two tropical land regions contains more intense cores. (3) Deep convective outflow occurs at a higher level when the midtroposphere is more humid and the convective system size is smaller. The convective system size dependence is postulated to be related to convective lifecycle, highlighting the importance of cloud life stage information in interpretation of snapshot measurements by satellite. Finally, implications of the study to global modeling are discussed.

The fractional water vapor changes under global warming across 14 Coupled Model Intercomparison Project Phase 5 simulations are analyzed. We show that the mean fractional water vapor changes under global warming in the tropical upper troposphere between 300 and 100 hPa range from 12.4 to 28.0 %/K across all models while the fractional water vapor changes are about 5–8 %/K in other regions and at lower altitudes. The “upper-tropospheric amplification” of the water vapor change is primarily driven by a larger temperature increase in the upper troposphere than in the lower troposphere per degree of surface warming. The relative contributions of atmospheric temperature and relative humidity changes to the water vapor change in each model vary between 71.5 to 131.8 % and 24.8 to −20.1 %, respectively. The inter-model differences in the water vapor change is primarily caused by differences in temperature change, except over the inter-tropical convergence zone within 10°S–10°N where the model differences due to the relative humidity change are significant. Furthermore, we find that there is generally a positive correlation between the rates of water vapor change for long-tem surface warming and those on the interannual time scales. However, the rates of water vapor change under long-term warming have a systematic offset from those on the inter-annual time scales and the dominant contributor to the differences also differs for the two time scales, suggesting caution needs to be taken when inferring long-term water vapor changes from the observed interannual variations.

Upper tropospheric water vapor (UTWV) plays a critical role in amplifying global warming caused by increasing greenhouse gases, yet it is one of the most poorly simulated quantities in climate models. It is not clear what physical processes play a central role in controlling the model errors in UTWV. We diagnose the UTWV simulation errors from AMIP models submitted to the CMIP5 project by using “A-Train” satellite observation and reanalysis data. We identify the relative contributions of errors in relative humidity (RH), temperature, and large-scale circulation (represented by vertical pressure velocity at 500 hPa, ω500) to the modeled UTWV errors over the tropics (30°N–30°S). It is found that models generally have positive biases in UTWV, except over the continental convective regions where negative biases predominate. The errors in the patterns and amplitudes of climatological UTWV are highly correlated with those in RH and ω500. The fractional UTWV errors show large positive errors over the large-scale descending regimes (0 300 K or ω500

International audience; Aerosols have a potentially large effect on climate, particularly through their interactions with clouds, but the magnitude of this effect is highly uncertain. Large volcanic eruptions produce sulfur dioxide, which in turn produces aerosols; these eruptions thus represent a natural experiment through which to quantify aerosol-cloud interactions. Here we show that the massive 2014-2015 fissure eruption in Holuhraun, Iceland, reduced the size of liquid cloud droplets—consistent with expectations—but had no discernible effect on other cloud properties. The reduction in droplet size led to cloud brightening and global-mean radiative forcing of around -0.2 watts per square metre for September to October 2014. Changes in cloud amount or cloud liquid water path, however, were undetectable, indicating that these indirect effects, and cloud systems in general, are well buffered against aerosol changes. This result will reduce uncertainties in future climate projections, because we are now able to reject results from climate models with an excessive liquid-water-path response.

This paper describes a novel use of A-Train observations to estimate vertical velocities for actively growing convective plumes and to relate them to cloud internal vertical structure. Convective vertical velocity is derived from time-delayed (1–2 min) IR measurements from MODIS and IIR. Convective vertical velocities are found to be clustered around 2–4 m/s but the distributions are positively skewed with long tails extending to larger values. Land convection during the 13:30 overpasses has higher vertical velocities than those during the 1:30 overpasses; oceanic convection shows the opposite, albeit smaller, contrast. Our results also show that convection with larger vertical velocity tends to transport larger precipitation-size particle and/or greater amount of water substance to higher altitude and produces heavier rainfall. Finally, we discuss the implications of this study for the designs of future space-borne missions that focus on fast-evolving processes such as those related to clouds and precipitation.

[1] Tropical overshooting deep convection (ODC) plays an important role in affecting the heat and constituent budgets of the upper troposphere and lower stratosphere. This study investigates the properties and behaviors of such intense deep convection using a combination of CloudSat observations and geostationary satellite data. Our study approaches the subject from two unique perspectives: first, W-band cloud profiling radar (CPR) observations from CloudSat are used, which add to our knowledge of the internal vertical structure of tropical ODC; second, each snapshot observation from CloudSat is cast into the time evolution of the convective systems through joint analysis of geostationary satellite data, which provides a lifecycle view of tropical ODC. Climatology of tropical ODC based on CloudSat data is first presented and compared with previous works. Various parameters from CloudSat observations pertaining to cloud vertical extent, convective intensity, and convective environment are analyzed. Although results broadly agree with previous studies, we show that CloudSat CPR is capable of capturing both small cloud particles and large precipitation-size particles, thus presenting a more complete depiction of the internal vertical structure of tropical ODC. Geostationary satellite observations are analyzed in conjunction with CloudSat data to identify the life stage of the convective systems (CSs) in which ODC is embedded. ODC associated with the growing, mature, and dissipating stage of the CSs represents, respectively, 66.2%, 33.4%, and 0.4% of the total population. Convective intensity of the ODC is found to be stronger during the growing stage than the mature stage.

[1] Water vapor measurements from Aura Microwave Limb Sounder (MLS, above 300 hPa) and Aqua Atmospheric Infrared Sounder (AIRS, below 300 hPa) are analyzed to study the variations of moisture during the 2006–2007 and 2009–2010 El Ninos. The 2006–2007 El Nino is an East Pacific (EP) El Nino, while the 2009–2010 El Nino is a Central Pacific (CP) El Nino or El Nino Modoki. Results show that these two types of El Nino events produce different patterns of water vapor anomalies over the tropical ocean, approximately resembling the cloud anomalies shown in Su and Jiang (2013). Regression of water vapor anomalies onto the Nino-3.4 SST for the A-Train period shows a clear “upper tropospheric amplification” of the fractional water vapor change, i.e., the ratio of the change in specific humidity to the layer-averaged specific humidity. Furthermore, tropical water vapor anomalies in different circulation regimes are examined. It is shown that the variations of water vapor during the 2006–2007 El Nino are mainly controlled by the thermodynamic component, whereas both dynamic and thermodynamic components control the water vapor anomalies during the 2009–2010 El Nino. GFDL AM2.1 model simulations of water vapor and cloud anomalies for the two El Ninos are compared with the satellite observations. In general, the model approximately reproduces the water vapor anomalies on both zonal and meridional planes but it produces too strong a cloud response in the mid- and lower troposphere. The model fails to capture the dynamic component of water vapor anomalies, particularly over the Indian Ocean.

This corrects the article DOI: 10.1038/nature22974.

[1] This study revisits an old concept in meteorology - level of neutral buoyancy (LNB). The classic definition of LNB is derived from the parcel theory and can be estimated from the ambient sounding (LNB_sounding) without having to observe any actual convective cloud development. In reality, however, convection interacts with the environment in complicated ways; it will eventually manage to find its own effective LNB and manifests it through detraining masses and developing anvils (LNB_observation). This study conducts a near-global survey of LNB_observation for tropical deep convection using CloudSat data and makes comparison with the corresponding LNB_sounding. The principal findings are as follows: First, although LNB_sounding provides a reasonable upper bound for convective development, correlation between LNB_sounding and LNB_observation is low suggesting that ambient sounding contains limited information for accurately predicting the actual LNB. Second, maximum mass outflow is located more than 3 km lower than LNB_sounding. Hence, from convective transport perspective, LNB_sounding is a significant overestimate of the “destination” height level of the detrained mass. Third, LNB_observation is consistently higher over land than over ocean, although LNB_sounding is similar between land and ocean. This difference is likely related to the contrasts in convective strength and environment between land and ocean. Finally, we estimate the bulk entrainment rates associated with the observed deep convection, which can serve as an observational basis for adjusting GCM cumulus parameterization.