Storm-centered infrared (IR) imagery of tropical cyclones (TCs) is related to the 850-hPa mean tangential wind at a radius of 500 km (V500) calculated from 6-hourly global numerical analyses for North Atlantic and eastern North Pacific TCs for 1995-2011. V500 estimates are scaled using the climatological vortex decay rate beyond 500 km to estimate the radius of 5 kt (1 kt 5 0.514 m s 21) winds (R5) or TC size. A much larger historical record of TC-centered IR imagery (1978-2011 is then used to estimate TC sizes and form a global TC size climatology. The basin-specific distributions of TC size reveal that, among other things, the eastern North Pacific TC basins have the smallest while western North Pacific have the largest TC size distributions. The life cycle of TC sizes with respect to maximum intensity shows that TC growth characteristics are different among the individual TC basins, with the North Atlantic composites showing continued growth after maximum intensity. Small TCs are generally located at lower latitudes, westward steering, and preferred in seasons when environmental low-level vorticity is suppressed. Large TCs are generally located at higher latitudes, poleward steering, and preferred in enhanced low-level vorticity environments. Postmaximum intensity growth of TCs occurs in regions associated with enhanced baroclinicity and TC recurvature, while those that do not grow much are associated with west movement, erratic storm tracks, and landfall at or near the time of maximum intensity. With respect to climate change, no significant long-term trends are found in the dataset of TC size.

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A new and improved method for estimating tropical-cyclone (TC) flight-level winds using globally and routinely available TC information and infrared (IR) satellite imagery is presented. The developmental dataset is composed of aircraft reconnaissance (1995-2012) that has been analyzed to a 1 km 3 108 polar grid that extends outward 165 km from the TC center. The additional use of an azimuthally average tangential wind at 500 km, based on global model analyses, allows the estimation of winds at larger radii. Analyses are rotated to a direction-relative framework, normalized by dividing the wind field by the observed maximum, and then decomposed into azimuthal wavenumbers in terms of amplitudes and phases. Using a single-field principal component method, the amplitudes and phases of the wind field are then statistically related to principal components of motion-relative IR images and factors related to the climatological radius of maximum winds. The IR principal components allow the wind field to be related to the radial and azimuthal variability of the wind field. Results show that this method, when provided with the storm location, the estimated TC intensity, the TC motion vector, and a single IR image, is able to estimate the azimuthal wavenumber 0 and 1 components of the wind field. The resulting wind field reconstruction significantly improves on the method currently used for satellitebased operational TC wind field estimates. This application has several potential uses that are discussed within.

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Vertical distributions of aerosol backscattering were obtained on Transport and Atmospheric Chemistry Near the Equator‐Atlantic (TRACE A) flights parallel to the west coast of Africa using the airborne differential absorption lidar (DIAL) instrument. Aerosol distributions on the flight of October 15, 1992 (from 22°S to 5.5°S) exhibit strong horizontal and vertical gradients. The top of the aerosol layer ranges from 3.5 to 5.7 km above sea level, while its thickness ranges from 1.4 to 4.5 km. The greatest aerosol loading generally occurs near 4.0‐ to 4.5‐km altitude between 8° and 12°S. Meteorological conditions are found to exert a major influence on the aerosol distributions. Dropsonde data along the flight track indicate numerous temperature inversions and stable layers in each sounding. The top of the aerosol region is associated with strong inversions due to subsidence. Five‐day backward trajectories are calculated along the flight track at vertical intervals of 1 km using global meteorological analyses. Trajectories arriving at most locations of large aerosol loading originate over southern Africa, where biomass burning is occurring and deep surface‐based mixed layers are common. Conversely, the air with less aerosol loading originates over the Atlantic Ocean. The exception is the northernmost segment of the flight above 3.5 km. Although this segment receives flow off Africa at these altitudes, lower level stable layers inhibit transport to higher levels. In addition, trajectories arriving at this part of the flight pass over a portion of Africa with reduced biomass burning and extensive deep convection that penetrates the stable layers.

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The increasing use of mobile phones (MPs) equipped with digital cameras and the ability to post images and information to the Internet in real time has significantly improved the ability to report events almost instantaneously. From the perspective of weather forecasters responsible for issuing severe weather warnings, the old adage holds that a picture is indeed worth a thousand words; a single digital image conveys significantly more information than a simple web-submitted text or phone-relayed report. Timely, quality-controlled, and value-added photography allows the forecaster to ascertain the validity and quality of storm reports. The posting of geolocated, time-stamped storm report photographs utilizing an MP application to U.S. National Weather Service (NWS) Weather Forecast Office (WFO) social media pages has generated recent positive feedback from forecasters. This study establishes the conceptual framework, architectural design, and pathway toward implementation of a formalized photo report (PR) system composed of 1) an MP application, 2) a processing and distribution system, and 3) the Advanced Weather Interactive Processing System II (AWIPS II) data plug-in software. The requirements and anticipated appearance of such a PR system are presented, along with considerations for possible additional features and applications that extend the utility of the system beyond the realm of severe weather applications.

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