Upper tropospheric water vapour and its interaction with cirrus clouds as seen from IAGOS long-term routine in situ observations.

IAGOS (In-service Aircraft for a Global Observing System) performs long-term routine in situ observations of atmospheric chemical composition (O3, CO, NOx, NOy, CO2, CH4), water vapour, aerosols, clouds, and temperature on a global scale by operating compact instruments on board of passenger aircraft. The unique characteristics of the IAGOS data set originate from the global scale sampling on air traffic routes with similar instrumentation such that the observations are truly comparable and well suited for atmospheric research on a statistical basis. Here, we present the analysis of 15 months of simultaneous observations of relative humidity with respect to ice (RHice) and ice crystal number concentration in cirrus (Nice) from July 2014 to October 2015. The joint data set of 360 hours of RHice-Nice observations in the global upper troposphere and tropopause region is analysed with respect to the in-cloud distribution of RHice and related cirrus properties. The majority of the observed cirrus is thin with Nice < 0.1 cm-3. The respective fractions of all cloud observations range from 90% over the mid-latitude North Atlantic Ocean and the Eurasian Continent to 67% over the subtropical and tropical Pacific Ocean. The in-cloud RHice distributions do not depend on the geographical region of sampling. Types of cirrus origin (in situ origin, liquid origin) are inferred for different Nice regimes and geographical regions. Most importantly, we found that in-cloud RHice shows a strong correlation to Nice with slightly supersaturated dynamic equilibrium RHice associated with higher Nice values in stronger updrafts.

[1]  M. Wendisch,et al.  ML-CIRRUS : The airborne experiment on natural cirrus and contrail cirrus with the high-altitude long-range research aircraft HALO , 2017 .

[2]  Volker Ebert,et al.  HAI, a new airborne, absolute, twin dual-channel, multi-phase TDLAS-hygrometer: background, design, setup, and first flight data , 2017 .

[3]  Klaus Pfeilsticker,et al.  ACRIDICON–CHUVA Campaign: Studying Tropical Deep Convective Clouds and Precipitation over Amazonia Using the New German Research Aircraft HALO , 2016 .

[4]  E. Mahieu,et al.  Validation of MOPITT carbon monoxide using ground-based Fourier transform infrared spectrometer data from NDACC , 2016 .

[5]  V. Freudenthaler,et al.  Properties of individual contrails: A compilation of observations and some comparisons , 2016 .

[6]  H. Wernli,et al.  A trajectory‐based classification of ERA‐Interim ice clouds in the region of the North Atlantic storm track , 2016 .

[7]  M. Riese,et al.  The need for accurate long-term measurements of water vapor in the upper troposphere and lower stratosphere with global coverage , 2016, Earth's future.

[8]  Jessica R. Meyer,et al.  The origin of midlatitude ice clouds and the resulting influence on their microphysical properties , 2015 .

[9]  Jessica R. Meyer,et al.  A microphysics guide to cirrus clouds – Part 1: Cirrus types , 2015 .

[10]  Volker Ebert,et al.  Quality assessment of MOZAIC and IAGOS capacitive hygrometers: insights from airborne field studies , 2015 .

[11]  Patrick Minnis,et al.  Properties of small cirrus ice crystals from commercial aircraft measurements and implications for flight operations , 2015 .

[12]  Martin Gallagher,et al.  Global-scale atmosphere monitoring by in-service aircraft – current achievements and future prospects of the European Research Infrastructure IAGOS , 2015 .

[13]  K. Shine,et al.  Ice supersaturation and the potential for contrail formation in a changing climate , 2015 .

[14]  J. Jensen,et al.  Distributions of ice supersaturation and ice crystals from airborne observations in relation to upper tropospheric dynamical boundaries , 2015 .

[15]  Jessica R. Meyer,et al.  Two decades of water vapor measurements with the FISH fluorescence hygrometer: a review , 2015 .

[16]  A. Petzold,et al.  Technical Note: Reanalysis of upper troposphere humidity data from the MOZAIC programme for the period 1994 to 2009 , 2014 .

[17]  C. Brenninkmeijer,et al.  Processes controlling water vapor in the upper troposphere/lowermost stratosphere: An analysis of 8 years of monthly measurements by the IAGOS‐CARIBIC observatory , 2014 .

[18]  Rolf Müller,et al.  Comparison of Fast In situ Stratospheric Hygrometer (FISH) measurements of water vapor in the upper troposphere and lower stratosphere (UTLS) with ECMWF (re)analysis data , 2014 .

[19]  P. Spichtinger.  Shallow cirrus convection – a source for ice supersaturation , 2014 .

[20]  A. Petzold,et al.  Evaluation of the MOZAIC Capacitive Hygrometer during the airborne field study CIRRUS-III , 2014 .

[21]  A. Heymsfield,et al.  Hemispheric comparison of cirrus cloud evolution using in situ measurements in HIAPER Pole‐to‐Pole Observations , 2014 .

[22]  M. Gallagher,et al.  The backscatter cloud probe – a compact low-profile autonomous optical spectrometer , 2013 .

[23]  Corinna Hoose,et al.  Heterogeneous ice nucleation on atmospheric aerosols: a review of results from laboratory experiments , 2012 .

[24]  Andrew Gettelman,et al.  Climate impacts of ice nucleation , 2012 .

[25]  Martin Riese,et al.  Impact of uncertainties in atmospheric mixing on simulated UTLS composition and related radiative effects , 2012 .

[26]  C. Stubenrauch,et al.  A global climatology of upper-tropospheric ice supersaturation occurrence inferred from the Atmospheric Infrared Sounder calibrated by MOZAIC , 2012 .

[27]  J. Thepaut,et al.  The ERA‐Interim reanalysis: configuration and performance of the data assimilation system , 2011 .

[28]  E. Fetzer,et al.  Cloudy and clear‐sky relative humidity in the upper troposphere observed by the A‐train , 2009 .

[29]  Jessica R. Meyer,et al.  Ice water content of Arctic, midlatitude, and tropical cirrus - Part 2: Extension of the database and new statistical analysis , 2008 .

[30]  A. Mangold,et al.  Ice supersaturations and cirrus cloud crystal numbers , 2008 .

[31]  K. Gierens,et al.  Modelling of cirrus clouds – Part 2: Competition of different nucleation mechanisms , 2008 .

[32]  D. Kley,et al.  An In-Flight Calibration Method for Near-Real-Time Humidity Measurements with the Airborne MOZAIC Sensor , 2008 .

[33]  K. Sassen,et al.  Global distribution of cirrus clouds from CloudSat/Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements , 2008 .

[34]  U. Lohmann,et al.  Impact of ice supersaturated regions and thin cirrus on radiation in the midlatitudes , 2007 .

[35]  P. Pilewskie,et al.  Effects of ice crystal habit on thermal infrared radiative properties and forcing of cirrus , 2007 .

[36]  Andrew Gettelman,et al.  The Global Distribution of Supersaturation in the Upper Troposphere from the Atmospheric Infrared Sounder , 2006 .

[37]  Manfred Wendisch,et al.  Impact of Cirrus Crystal Shape on Solar Spectral Irradiance: A Case Study for Subtropical Cirrus , 2005 .

[38]  J. Gayet,et al.  On the distribution of relative humidity in cirrus clouds , 2004 .

[39]  Klaus Gierens,et al.  The global distribution of ice‐supersaturated regions as seen by the Microwave Limb Sounder , 2003 .

[40]  R. Sausen,et al.  Determining the tropopause height from gridded data , 2003 .

[41]  U. Schumann,et al.  Water vapour measurements inside cirrus clouds in Northern and Southern hemispheres during INCA , 2002 .

[42]  W. Read,et al.  The statistical distribution law of relative humidity in the global tropopause region , 2002 .

[43]  B. Luo,et al.  Water activity as the determinant for homogeneous ice nucleation in aqueous solutions , 2000, Nature.

[44]  Klaus Gierens,et al.  On the size distribution of ice-supersaturated regions in the upper troposphere and lowermost stratosphere , 2000 .

[45]  B. Strauss,et al.  On the Transition of Contrails into Cirrus Clouds , 2000 .

[46]  Klaus Gierens,et al.  A distribution law for relative humidity in the upper troposphere and lower stratosphere derived from three years of MOZAIC measurements , 1999 .

[47]  D. Kley,et al.  Calibration and performance of automatic compact instrumentation for the measurement of relative humidity from passenger aircraft , 1998 .

[48]  John A. Pyle,et al.  Measurement of ozone and water vapor by Airbus in-service aircraft: The MOZAIC airborne program, an overview , 1998 .

[49]  D. Sonntag,et al.  Advancements in the field of hygrometry , 1994 .