Preprints
https://doi.org/10.5194/amt-2021-89
https://doi.org/10.5194/amt-2021-89

  19 Apr 2021

19 Apr 2021

Review status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

Boundary layer water vapour statistics from high-spatial-resolution spaceborne imaging spectroscopy

Mark T. Richardson1,2, David R. Thompson1, Marcin J. Kurowski1, and Matthew D. Lebsock1 Mark T. Richardson et al.
  • 1Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
  • 2Department of Atmospheric Science, Colorado State University, Fort Collins, CO 90095, USA

Abstract. Daytime clear-sky total column water vapour (TCWV) is commonly retrieved from visible and shortwave infrared reflectance (VSWIR) measurements, and upcoming missions such as the Earth Surface Mineral Dust Source Investigation (EMIT) will offer unprecedented horizontal resolution of order 30–80 m. We provide evidence that for convective planetary boundary layers (PBLs), spatial variability in TCWV corresponds to variability in PBL water vapour. Using synthetic optimal estimation retrievals applied to Large Eddy Simulation (LES) output, we show that EMIT can retrieve horizontal variability in PBL water vapour, provided that the domain surface is uniformly composed of either vegetated surfaces or mineral surfaces. Random retrieval errors are easily quantified and removed, but biases from −7 % to +34 % remain in retrieved spatial standard deviation and are primarily related to the retrieval’s assumed atmospheric profiles. Future retrieval development could greatly mitigate these errors. Finally, we account for changing solar zenith angle (SZA) from 15–60° and show that the non-vertical solar path destroys the correspondence between footprint retrieved TCWV and the true TCWV directly above that footprint. Even at the 250 m horizontal resolution regularly obtained by current sensors, the derived maps correspond poorly to true TCWV at the pixel-scale, with r2 < 0.6 at SZA = 30°. However, the derived histograms of TCWV in an area are closely related to the true histograms of TCWV at the nominal footprint resolution. Upcoming VSWIR instruments, primarily targeting surface properties, can therefore offer new information on PBL water vapour spatial statistics to the atmospheric community.

Mark T. Richardson et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-89', Anonymous Referee #1, 25 May 2021
    • AC1: 'Reply on RC1', Mark Richardson, 23 Jun 2021
  • RC2: 'Comment on amt-2021-89', Anonymous Referee #2, 02 Jun 2021
    • AC2: 'Reply on RC2', Mark Richardson, 23 Jun 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-89', Anonymous Referee #1, 25 May 2021
    • AC1: 'Reply on RC1', Mark Richardson, 23 Jun 2021
  • RC2: 'Comment on amt-2021-89', Anonymous Referee #2, 02 Jun 2021
    • AC2: 'Reply on RC2', Mark Richardson, 23 Jun 2021

Mark T. Richardson et al.

Mark T. Richardson et al.

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Short summary
Upcoming hyperspectral imagers will take images with spatial resolution as fine as 30 m. They can retrieve column water vapour and we show evidence that from these column measurements you can get statistics of planetary boundary layer (PBL) water vapour. This is important information for climate models that need to account for sub-grid mixing of water vapour near the surface in their PBL schemes.