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NASA NTRS1980

Weather and climate needs for Lidar observations from space and concepts for their realization

The spectrum of weather and climate needs for Lidar observations from space is discussed with emphasis on the requirements for wind, temperature, moisture, and pressure data. It is shown that winds are required to realistically depict all atmospheric scales in the tropics and the smaller scales at higher latitudes, where both temperature and wind profiles are necessary. The need for means to estimate air-sea exchanges of sensible and latent heat also is noted. A concept for achieving this through a combination of Lidar cloud top heights and IR cloud top temperatures of cloud streets formed during cold air outbreaks over the warmer ocean is outlined. Recent theoretical feasibility studies concerning the profiling of temperatures, pressure, and humidity by differential absorption Lidar (DIAL) from space and expected accuracies are reviewed. An alternative approach to Doppler Lidar wind measurements also is presented. The concept involves the measurement of the displacement of the aerosol backscatter pattern, at constant heights, between two successive scans of the same area, one ahead of the spacecraft and the other behind it a few minutes later. Finally, an integrated space Lidar system capable of measuring temperature, pressure, humidity, and winds which combines the DIAL methods with the aerosol pattern displacement concept is described.

Atlas, D.↗

NASA NTRS1988

An Earth radiation budget climate model

A 2-D Earth Radiation Budget Climate Model has been constructed from an OLWR (Outgoing Longwave Radiation) model and an Earth albedo model. Each of these models uses the same cloud cover climatology modified by a factor GLCLC which adjusts the global annual average cloud cover. The two models are linked by a set of equations which relate the cloud albedos to the cloud top temperatures of the OLWR model. These equations are derived from simultaneous narrow band satellite measurements of cloud top temperature and albedo. Initial results include global annual average values of albedo and latitude/longitude radiation for 45 percent and 57 percent global annual average cloud cover and two different forms of the cloud albedo-cloud top temperature equations.

Bartman, Fred L.↗

NASA NTRS1983

Thunderstorm cloud top observations using satellite stereoscopy

The present investigation has as objective to take a detailed look at the intense squall line over Oklahoma on May 2-3, 1979, using GOES stereoscopy combined with GOES infrared data. The synoptic situation and data sources are considered along with the stereoscopically observed cloud top ascent rates. Cloud top observations of intense thunderstorms are discussed, taking into account a contouring technique, the interpretation of infrared cloud top temperature patterns, and small-scale structure and its variability. It is found that GOES IR cloud top temperatures grossly underestimate the actual cloud top height observed stereoscopically, especially for immature storms. It is difficult to define growing storms below about 10 km in the GOES infrared data.

Mack, R. A.↗

NASA NTRS1982

Satellite infrared imagery, rawinsonde data, and gravity wave remote sensing of severe convective storms

GOES digital infrared data during the time period between two hours before the touchdown of tornado and the tornado touchdown time were used in this study. Comparison between tornado-associated clouds and non-tornado-associated clouds indicates that the difference between overshooting cloud top temperature and the tropopause temperature, or how much the cloud has penetrated above the tropopause, rather than either the absolute temperature of penetrative cloud top or the height of the top of overshooting turret is significant for the possible formation of severe storms. The penetrative overshooting cloud top collapses about 15 to 30 minutes before the touchdown of tornado. Gravity waves were detected from the severe convective storms.

Hung, R. J.↗

NASA NTRS1981

Stereographic observations from geosynchronous satellites - An important new tool for the atmospheric sciences

Observations of cloud geometry using scan-synchronized stereo geostationary satellites having images with horizontal spatial resolution of approximately 0.5 km, and temporal resolution of up to 3 min are presented. The stereo does not require a cloud with known emissivity to be in equilibrium with an atmosphere with a known vertical temperature profile. It is shown that absolute accuracies of about 0.5 km are possible. Qualitative and quantitative representations of atmospheric dynamics were shown by remapping, display, and stereo image analysis on an interactive computer/imaging system. Applications of stereo observations include: (1) cloud top height contours of severe thunderstorms and hurricanes, (2) cloud top and base height estimates for cloud-wind height assignment, (3) cloud growth measurements for severe thunderstorm over-shooting towers, (4) atmospheric temperature from stereo heights and infrared cloud top temperatures, and (5) cloud emissivity estimation. Recommendations are given for future improvements in stereo observations, including a third GOES satellite, operational scan synchronization of all GOES satellites and better resolution sensors.

Hasler, A. F.↗

NASA NTRS2007

Multi-Sensor Data from A-Train Instruments Brought Together for Atmospheric Research

The A-Train is comprised of a series of instruments, developed independently, that measure highly related atmospheric components along the same flight path. In order to intercompare data from this multitude of sensors, researchers must access, subset, visualize, analyze and correlate distributed atmosphere measurements from the various A-Train instruments. The A-Train Data Depot (ATDD) has been operational for over a year, successfully performing the aforementioned functions on behalf of researchers, thus providing co-registered data from the Cloudsat, CALIOP, AIRS, and MODIS instruments for further intercomparisons. Of late, significant data from OM1 and POLDER are now included in the 'depot'. By specifying the desired spatial and temporal range, the researcher can subset, visualize, co-register, and access multi-sensor A-Train data related to: Cloud, aerosol, atmospheric temperature, and water vapor parameters (vertical profile visualizations); Cloud Pressure, cloud top temperature, water vapor, cloud optical thickness, and aerosol products (horizontal strips subsetted +/- 100km from the profile visualizations), and; Cloud pressure parameters (2-D line plots overlayed on the vertical profiles). All data is plotted using the GIOVANNI data exploration tool. A new feature of GIOVANNI is its ability to have collocated and subsetted data sets as well as PNG image files downloaded to the researcher's computing facility. By providing a convenient way to visualize and acquire multi-sensor data, ATDD affords users more time and effort to further their research.

Smith, Peter M.↗

DOE OSTI2023

Asymmetries in cloud microphysical properties ascribed to sea ice leads via water vapour transport in the central Arctic

To investigate the influence of sea ice openings like leads on wintertime Arctic clouds, the air mass transport is exploited as a heat and humidity feeding mechanism which can modify Arctic cloud properties. Cloud microphysical properties in the central Arctic are analysed as a function of sea ice conditions during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in 2019–2020. The Cloudnet classification algorithm is used to characterize the clouds based on remote sensing observations and the atmospheric thermodynamic state from the observatory on board the research vessel (RV) Polarstern. To link the sea ice conditions around the observational site with the cloud observations, the water vapour transport (WVT) being conveyed towards RV Polarstern has been utilized as a mechanism to associate upwind sea ice conditions with the measured cloud properties. This novel methodology is used to classify the observed clouds as coupled or decoupled to the WVT based on the location of the maximum vertical gradient of WVT height relative to the cloud-driven mixing layer. Only a conical sub-sector of sea ice concentration (SIC) and the lead fraction (LF) centred on the RV Polarstern location and extending up to 50 km in radius and with an azimuth angle governed by the time-dependent wind direction measured at the maximum WVT is related to the observed clouds. We found significant asymmetries for cases when the clouds are coupled or decoupled to the WVT and selected by LF regimes. Liquid water path of low-level clouds is found to increase as a function of LF, while the ice water path does so only for deep precipitating systems. Clouds coupled to WVT are found to generally have a lower cloud base and larger thickness than decoupled clouds. Thermodynamically, for coupled cases the cloud-top temperature is warmer and accompanied by a temperature inversion at the cloud top, whereas the decoupled cases are found to be closely compliant with the moist adiabatic temperature lapse rate. The ice water fraction within the cloud layer has been found to present a noticeable asymmetry when comparing coupled versus decoupled cases. This novel approach of coupling sea ice to cloud properties via the WVT mechanism unfolds a new tool to study Arctic surface–atmosphere processes. With this formulation, long-term observations can be analysed to enforce the statistical significance of the asymmetries. Furthermore, our results serve as an opportunity to better understand the dynamic linkage between clouds and sea ice and to evaluate its representation in numerical climate models for the Arctic system.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1982

Skylab near-infrared observations of clouds indicating supercooled liquid water droplets

Orographically-induced lee-wave clouds were observed over New Mexico by a multichannel scanning radiometer on Skylab during December 1973. Channels centered at 0.83, 1.61 and 2.125 microns were used to determine the cloud optical thickness, thermodynamic phase and effective particle size. An additional channel centered at 11.4 microns was used to determine cloud-top temperature, which was corroborated through comparison with the stereographically determined cloud top altitudes and conventional temperature soundings. Analysis of the measured near-infrared reflection functions at 1.61 and 2.125 microns are most easily interpreted as indicating the presence of liquid-phase water droplets. This interpretation is not conclusive even after considerable effort to understand possible sources for misinterpretation. However, if accepted the resulting phase determination is considered anomalous due to the inferred cloud-top temperatures being in the -32 to -47 C range. Theory for the homogeneous nucleation of pure supercooled liquid water droplets predicts very short lifetimes for the liquid phase at these cold temperatures. A possible explanation for the observations is that the wave-clouds are composed of solution droplets. Impurities in the cloud droplets could decrease the homogeneous freezing rate for these droplets, permitting them to exist for a longer time in the liquid phase, at the cold temperatures found.

Curran, R. J.↗

DOE OSTI2024

Parallax-corrected VISST-derived pixel-level products from satellite GOES-16

The NASA Langley group led by William Smith produced GOES-16 satellite cloud retrievals over an approximate 10 by 10 degree region over the CACTI field campaign location. These retrievals are described here: https://www.arm.gov/capabilities/vaps/visst and are available for download here . They use algorithms historically called VISST that are now referred to as SatCORPS. More information can be found in Trepte et al. (2019), Minnis et al. (2021), and Yost et al. (2021). If using this dataset, please cite these references, the CACTI VISST dataset DOI found at the download link above, and this dataset’s DOI. The CACTI VISST pixel-level retrievals are on a 2 km spatial grid and available every 15 minutes (every 10 minutes late in the campaign), producing 21,765 files for the entire field campaign between October 2018 and April 2019. They are not corrected for parallax error, which is an offset in the actual geographical location of a cloud above the surface due to the satellite viewing the cloud partly from the side off nadir. This dataset applies a correction for parallax using the location relative to the satellite and the retrieved cloud top height above the surface, which allows the dataset to be geo-located with surface-based observations. The parallax correction for each location depends on the longitude, latitude and cloud top height above ground level (AGL) for that longitude and latitude in the original VISST files. The cloud top height AGL requires first computing the surface elevation at each VISST grid point. Data from the Advanced Spaceborne Thermal Emission and Reflection (ASTER) Global Digital Elevation Map Version 3 at 30-m resolution is projected onto the VISST grid using conservative coarsening (conserving surface elevation) in the xESMF Python package. The surface elevation is then subtracted from the VISST-retrieved cloud top height above mean sea level. These cloud top heights AGL are then combined with longitude and latitude to estimate the latitude and longitude corrections. Due to variability in cloud top height, the parallax shifts produce an irregular grid of values since higher cloud tops are shifted further than lower cloud tops. A ball tree-based neighbor search with Haversine distance is performed using the Python-based scikit-learn library to find the nearest VISST grid point to each parallax correction-shifted point. The data value of the shifted point is then assigned to that VISST grid point. In this manner, the irregular geographical shifts to correct for parallax are projected back to the rectilinear VISST grid. Because relatively higher clouds should obscure lower clouds, the variable values for the highest cloud top are preferentially chosen if two or more values are assigned to a grid point. The parallax correction should be viewed as an improved but still imperfect estimation of the cloud top locations, largely because the cloud top height is an imperfect retrieval. Please see the attached README document for further information. Users are encouraged to contact the authors with any additional questions.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1980

Predicting tropical cyclone intensity using satellite-measured equivalent blackbody temperatures of cloud tops

A relationship between maximum winds and satellite-measured equivalent blackbody temperatures near tropical cyclones is investigated with data from both the Atlantic and western North Pacific areas. This investigation revealed not only a significant correlation between satellite-derived equivalent blackbody temperatures and maximum winds but also a strong lag relationship between these temperatures and maximum winds. From this latter relationship a regression technique was developed to forecast 24-h changes of the maximum winds for weak (maximum winds less than or equal to 65 kt) and strong (maximum winds greater than 65 kt) tropical cyclones by utilizing the equivalent blackbody temperatures around the storm alone, together with changes in maximum winds during the preceding 24 h and the current maximum winds. Testing of these equations with independent data showed that the mean errors of forecasts made by the equations are lower than the errors in forecasts made by persistence techniques.

Gentry, R. C.↗

NASA NTRS1990

Stratocumulus cloud height variations determined from surface and satellite observations

Determination of cloud-top heights from satellite-inferred cloud-top temperatures is a relatively straightforward procedure for a well-behaved troposphere. The assumption of a monotonically decreasing temperature with increasing altitude is commonly used to assign a height to a given cloud-top temperature. In the hybrid bispectral threshold method, or HBTM, Minnis et al. (1987) assume that the lapse rate for the troposphere is -6.5/Kkm and that the surface temperature which calibrated this lapse rate is the 24 hour mean of the observed or modeled clear-sky, equivalent blackbody temperature. The International Satellite Cloud Climatology Project (ISCCP) algorithm (Rossow et al., 1988) attempts a more realistic assignment of height by utilizing interpolations of analyzed temperature fields from the National Meteorological Center (NMC) to determine the temperature at a given level over the region of interest. Neither these nor other techniques have been tested to any useful extent. The First ISCCP Regional Experiment (FIRE) Intensive Field Observations (IFO) provide an excellent opportunity to assess satellite-derived cloud height results because of the availability of both direct and indirect cloud-top altitude data of known accuracy. The variations of cloud-top altitude during the Marine Stratocumulus IFO (MSIFO, June 29 to July 19, 1987) derived from surface, aircraft, and satellite data are examined.

Minnis, Patrick↗

NASA NTRS1983

The 1980 stratospheric-tropospheric exchange experiment

Data are presented from the Stratospheric-Tropospheric Water Vapor Exchange Experiment. Measurements were made during 11 flights of the NASA U-2 aircraft which provided data from horizontal traverser and samplings in and about the tops of extensive cirrus-anvil clouds produced by overshooting cumulus turrets. Aircraft measurements were made of water vapor, ozone, ambient and cloud top temperature, fluorocarbons, nitrous oxide, nitric acid, aerosols, and ice crystal populations. Balloonsondes were flown about twice daily providing data on ozone, wind fields, pressure and temperature to altitudes near 30 km. Satellite photography provided detailed cloud and cloud top temperature information. Descriptions of individual experiments and detailed compilations of all results are provided.

Margozzi, A. P.↗

DOE OSTI2023

Vertical Structure and Ice Production Processes of Shallow Convective Postfrontal Clouds over the Southern Ocean in MARCUS. Part II: Modeling Study

Abstract Part I of this series presented a detailed overview of postfrontal mixed-phase clouds observed during the Measurements of Aerosols, Radiation, and Clouds over the Southern Ocean (MARCUS) field campaign. In Part II, we focus on a multiday (23–26 February 2018) case with the aim of understanding ice production as well as model sensitivity to ice process parameterizations using the Weather Research and Forecasting (WRF) Model. The control simulation with the Predicted Particle Properties (P3) microphysics scheme underestimates the ice content and overestimates the supercooled liquid water content, contrary to the bias common in global climate models. The simulations targeted at ice production processes show negligible sensitivity to cloud droplet number concentrations. Further, neither increasing ice nuclei particle (INP) concentrations to an unrealistic level nor adjusting it to MARCUS field estimations alone guarantees more ice production in the model. However, the simulated clouds are found to be highly sensitive to the implementation of immersion freezing, the thresholding of condensation/deposition freezing initiation, and the rime splintering process. By increasing immersion freezing of cloud droplets, relaxing thresholds for condensation/deposition freezing, or removing rime splintering thresholds, the model significantly improves its performance in producing ice. The relaxation of the immersion freezing temperature threshold to the observed cloud-top temperature suggests an in-cloud seeder–feeder mechanism. The results of this work call for an increase in observations of INP, especially over the remote Southern Ocean and at relatively high temperatures, and measurements of ice particle size distributions to better constrain ice nucleating processes in models.

Meteorology & Atmospheric Sciences↗

NASA NTRS2017

Global Statistics of Microphysical Properties of Cloud-Top Ice Crystals

Ice crystals in clouds are highly complex. Their sizes, macroscale shape (i.e., habit), mesoscale shape (i.e., aspect ratio of components) and microscale shape (i.e., surface roughness) determine optical properties and affect physical properties such as fall speeds, growth rates and aggregation efficiency. Our current understanding on the formation and evolution of ice crystals under various conditions can be considered poor. Commonly, ice crystal size and shape are related to ambient temperature and humidity, but global observational statistics on the variation of ice crystal size and particularly shape have not been available. Here we show results of a project aiming to infer ice crystal size, shape and scattering properties from a combination of MODIS measurements and POLDER-PARASOL multi-angle polarimetry. The shape retrieval procedure infers the mean aspect ratios of components of ice crystals and the mean microscale surface roughness levels, which are quantifiable parameters that mostly affect the scattering properties, in contrast to a habit. We present global statistics on the variation of ice effective radius, component aspect ratio, microscale surface roughness and scattering asymmetry parameter as a function of cloud top temperature, latitude, location, cloud type, season, etc. Generally, with increasing height, sizes decrease, roughness increases, asymmetry parameters decrease and aspect ratios increase towards unity. Some systematic differences are observed for clouds warmer and colder than the homogeneous freezing level. Uncertainties in the retrievals will be discussed. These statistics can be used as observational targets for modeling efforts and to better constrain other satellite remote sensing applications and their uncertainties.

Van Diedenhoven, Bastiaan↗

NASA NTRS1985

Measuring Clouds With Microwaves and Infrared

Combination of microwave and infrared measurements from satellites yields data from which thicknesses and temperature of clouds inferred. Microwave radiation measured by satellite used to determine thickness of cloud and difference between cloud-top temperature and mean temperature of interior. Technique extends capability of previously established method in which infrared radiation returned to satellite by cloud used to determine temperature and altitude of cloud top and fractional area of Earth covered by cloud.

Pandey, P. C.↗

NASA NTRS1985

Retrieval of cloud cover parameters from multispectral satellite images

A technique is described for extracting cloud cover parameters from multispectral satellite radiometric measurements. Utilizing three channels from the AVHRR (Advanced Very High Resolution Radiometer) on NOAA polar orbiting satellites, it is shown that one can retrieve four parameters for each pixel: cloud fraction within the FOV, optical thickness, cloud-top temperature and a microphysical model parameter. The last parameter is an index representing the properties of the cloud particle and is determined primarily by the radiance at 3.7 microns. The other three parameters are extracted from the visible and 11 micron infrared radiances, utilizing the information contained in the two-dimensional scatter plot of the measured radiances. The solution is essentially one in which the distributions of optical thickness and cloud-top temperature are maximally clustered for each region, with cloud fraction for each pixel adjusted to achieve maximal clustering.

Arking, A.↗

NASA NTRS1974

Correlation between cloud thickness and brightness using Nimbus 4 THIR data /11.5-micron channel/ and ATS 3 digital data

Nimbus 4 data (11.5-micron) channel and ATS 3 digitized data were analyzed for three days during April and May 1970. Cloud-top temperature, as measured by the 11.5-micron channel of the satellite radiometer, shows a close negative correlation with cloud brightness measured by the ATS 3 satellite. This is especially true in well-developed cumulonimbus clouds. An estimate of cloud heights corresponding to cloud-top temperature was obtained by using radiosonde data and radar images, and the relationships between the cloud thickness and brightness counts were derived for the cumulonimbus clouds.

Park, S.-U.↗

NASA NTRS1986

The relationship between satellite measured convective bursts and tropical cyclone intensification

High temporal resolution satellite IR measurements are used to analyze the relationship between the mean temperature of cloud canopy tops and the future maximum winds of Atlantic Ocean tropical cyclones. The measurements showed that prolonged surges of intense convection developed in the rear region surrounding cyclone depression centers before the maximum winds initially increased. When surges lasted for 9 hr or more, and the cloud-top temperature within 222 km of the cyclone centers was 238 K or less, then 71 percent of the time the maximum winds increased by 5 m/s or more within 24 hr. When intense convection was not present, similar maximum wind increases occurred only 37 percent of the time.

Steranka, J.↗