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Edoardo Mazza and Shuyi S. Chen

Abstract

The formation of tropical cyclones (TC) in unfavorable large-scale environments remains a challenge for TC forecasting. Tropical Storm (TS) Cindy (2017) formed at 1800 UTC 20 June in the Gulf of Mexico despite strong vertical wind shear, low mid-tropospheric relative humidity, and poorly organized convection. A key to TC genesis is the initial development of a warm core within an emergent cyclonic vortex, a process which occurs on small spatial scales and is often difficult to observe. TS Cindy was observed during the Convective Processes Experiment (CPEX) field campaign in 2017 by the NASA DC-8 aircraft, equipped with a Doppler wind lidar, precipitation radar, and GPS dropsondes. This study combines CPEX observations and a cloud-resolving, fully-coupled atmosphere-wave-ocean numerical simulation to investigate the formation of TS Cindy. Prior to TC genesis, a shallow cyclonic circulation was embedded in a deep layer of west-southwesterly flow associated with an upper-level trough. Within the disturbance, a warm and dry anomaly was observed by dropsondes near the center of the cyclonic circulation, with a maximum at about the 2.5 km level. The temperature perturbation reaches 5°C along with a dew point temperature depression of 8°C in the coupled model simulation. Backward trajectory analysis shows that subsidence is primarily associated with a thermally indirect circulation along the western flank of the storm. Air parcels descend more than 1000 m towards the lower troposphere while warming up by 9-12°C. The subsidence-induced virtual temperature perturbation in the 1.5-3.5 km layer accounts for 50 % of the sea-level pressure depression. Subsidence warming therefore played a key role in the genesis of TS Cindy.

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Tetsu Sakai, Narihiro Orikasa, Tomohiro Nagai, Masataka Murakami, Kenichi Kusunoki, Kazumasa Mori, Akihiro Hashimoto, Takatsugu Matsumura, and Takashi Shibata

on the particle size, shape, and chemical composition. For example, based on field observations ( Ferrare et al. 2001 ; Anderson et al. 2000 ) and theoretical calculations ( Ackermann 1998 ), the values for submicrometer-sized aerosols are generally higher than approximately 30 sr. Meanwhile, the values for the supermicrometer-sized ice crystals and water droplets are generally lower than 30 sr ( Sakai et al. 2003 ). Since the lidar was vertically pointing in this study, the δ and S values

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T. J. Swissler, P. Hamill, M. Osborn, P. B. Russell, and M. P. McCormick

.4 months, versus 10.4 and7.9 months for Nr>o. ls and Nr>o.25. The modeling technique is used to derive a time series of dustsonde-inferred peak backscatter mixingratio, which agrees very well with the lidar-measured series. The best overall agreement for 1974-80 isachieved with a mixture of refractive indices corresponding to aqueous sulfuric acid at about 210 K withan acid-weight fraction between 0.6 and 0.85.1. Introduction Experimental observations of the stratosphericaerosol layer have

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Taneil Uttal, Janet M. Intrieri, Wynn L. Eberhard, Eugene E. Clothiaux, and Thomas P. Ackerman

estimates of frequency of occurrence and amount of upper level clouds from observations at ground stations and ship-borne stations. Atmos. Oceanic Phys., 28 (5), 367-377. --, and , 1993: On the climatology of upper-layer 'clouds. J. Climate, 6, 1812-1821.Pal, S. R., W. Steinbrecht, and A. I. Carswell, 1992: Automated method for lidar determination of cloud base height and vertical extent. Appl. Opt., 31, 1488-1494.Parango, F., J. F. Boatman, H. Siervering, S

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J. M. Intrieri, W. L. Eberhard, T. Uttal, J. A. Shaw, J. B. Snider, Y. Han, B. W. Orr, and S. Y. Matrosov

instance, compared to longerwavelength radars, the signal from ground clutter is notas strong, thereby allowing observations within 100 mor so of the radar. At the same time, 8-mm radars willreadily penetrate optically thick clouds, allowing thedetection of cirrus clouds that are above layers of liquidwater and/or precipitation that would attenuate the signal from lidars or shorter wavelength radars. The radar dwell times for the FIRE II project werethree seconds, which represented a good

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Robert M. Banta, Lisa D. Olivier, and David H. Levinson

preliminary results ofthe experiment were described by Intrieri et al. (1990).Figure 1 shows the surrounding terrain and locationof the sensors. In addition to the instrumentation deployed over land, a ship, the R/V Silver Prince, servedas a platform for surface observations and rawinsondeascents during daylight hours on eight weekdays duringLASBEX. As discussed in section 1, the experimentfeatured two kinds of remote sensing instruments,WPL's Doppler lidar and an array of Doppler sodars.To supplement the

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Zhien Wang and Kenneth Sassen

derived from the Raman channel in the lower cloud portion and/or with the constraint of total optical depth ( Young 1995 ). To improve the signal-to-noise ratio of the lidar signal, a 10-min sliding average is applied to the Raman lidar data. The effect of multiple scattering on σ retrieval is not considered in this study, and this may cause the underestimation of visible cloud optical depth ( τ ) and average σ. However, we consider this effect as not very significant for high cloud observations

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C. M. R. Platt, R. T. Austin, S. A. Young, and A. J. Heymsfield

before the start of the monsoon season (e.g., Keenan et al. 1990 , 1994 , 2000 ). In this paper, we describe light detecting and ranging (lidar) and infrared radiometer observations on four storm anvils that were advected over the observational site. The experiment also included various radars ( Sekelsky et al. 1999 ) and a microwave radiometer that measured water vapor path and liquid water path. In Part I of this article, Platt et al. (2002 , hereafter Part I) describe the properties of

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H. Eisele, H. E. Scheel, R. Sladkovic, and T. Trickl

. However, due to the high costs, flight operations are limited to case studies and will not easily permit a dense coverage of stratosphere–troposphere exchange. At IFU, intensified observations of stratosphere–troposphere ozone transfer were started in January 1996, using the second-generation stationary lidar completed in 1995. The efforts have been carried out within the VOTALP (Vertical Ozone Transport in the Alps) project funded by the European Union. To establish such a work package within an

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A. H. Manson

(Vincent 1984; Chanin and Hauchcorne1981; Manson and Meek 1990). Rocket data generally have no (or uncertain) periods (e.g.,Philbrick et al. 1983). Finally, observed Xz (109) from 34 days in summer and winter 1981-86from lidar observations (observed period) are shown with toning (Gardner and Voelz 1987 ).measured lidar )tz of small value agree with the smallestXz from the less direct radar technique, suggesting thatthe two techniques are complementary. It should also be noted that the Urbana group

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