Lidar determinations of extinction in stratus clouds

Lindberg, James D.; Lentz, William J.; Measure, Edward M.; Rubio, Robert

doi:10.1364/ao.23.002172

Cited by 13 publications

(7 citation statements)

References 1 publication

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“…Four representations of extinction profiles are pictured: a LIDAR-retrieved σ -profile in the not-fully-attenuated region (red crosses), the theoretical LIDAR profile through the cloud layer (black solid), the not-attenuated extinction profile through the entire cloud layer (green dashed) as it could be retrieved by measurements made by particulate spectrometers carried aloft by tethered balloons (e.g. Lindberg et al, 1984) and the extrapolated σ -points as a result of the y = C x b curve-fit (blues crosses). The error related to the curve-fit to retrieve N represents a major source of uncertainty, i.e.…”

Section: Level 2: Cdncmentioning

confidence: 99%

Ground-based retrieval of continental and marine warm cloud microphysics

Martucci

O’Dowd

2011

Atmos. Meas. Tech.

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Abstract.A technique for retrieving warm cloud microphysics using synergistic ground based remote sensing instruments is presented. The SYRSOC (SYnergistic Remote Sensing Of Cloud) technique utilises a K a -band Doppler cloud RADAR, a LIDAR (or ceilometer) and a multichannel microwave radiometer. SYRSOC retrieves the main microphysical parameters such as cloud droplet number concentration (CDNC), droplets effective radius (r eff ), cloud liquid water content (LWC), and the departure from adiabatic conditions within the cloud. Two retrievals are presented for continental and marine stratocumulus advected over the Mace Head Atmospheric Research Station. Whilst the continental case exhibited high CDCN (N = 382 cm −3 ; 10th-to90th percentile [9.4-842.4] cm −3 ) and small mean effective radius (r eff = 4.3; 10th-to-90th percentile [2.9-6.5] µm), the marine case showed low CDNC and large mean effective radius (N = 25 cm −3 , 10th-to-90th percentile [1.5-69] cm −3 ; r eff = 28.4 µm, 10th-to-90th percentile [11.2-42.7] µm) as expected since continental air at this location is typically more polluted than marine air. The mean LWC was comparable for the two cases (continental: 0.19 g m −3 ; marine: 0.16 g m −3 ) but the 10th-90th percentile range was wider in marine air (continental: 0.11-0.22 g m −3 ; marine: 0.01-0.38 g m −3 ). The calculated algorithm uncertainty for the continental and marine case for each variable was, respectively, σ N = 161.58 cm −3 and 12.2 cm −3 , σ r eff = 0.86 µm and 5.6 µm, σ LWC = 0.03 g m −3 and 0.04 g m −3 . The retrieved CDNC are compared to the cloud condensation nuclei concentrations and the best agreement is achieved for a supersaturation of 0.1 % in the continental case and between 0.1 %-0.75 % for the marine stratocumulus. The retrieved r eff at the top of the clouds are compared to the MODIS satellite r eff : 7 µm (MODIS) vs. 6.2 µm (SYRSOC) and 16.3 µm (MODIS)Correspondence to: G. Martucci (giovanni.martucci@nuigalway.ie) vs. 17 µm (SYRSOC) for continental and marine cases, respectively. The combined analysis of the CDNC and the r eff , for the marine case shows that the drizzle modifies the droplet size distribution and r eff especially if compared to r MOD eff . The study of the cloud subadiabaticity and the LWC shows the general sub-adiabatic character of both clouds with more pronounced departure from adiabatic conditions in the continental case than in the marine.

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Section: Level 2: Cdncmentioning

confidence: 99%

Ground-based retrieval of continental and marine warm cloud microphysics

Martucci

O’Dowd

2011

Atmos. Meas. Tech.

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“…In the remaining cases, we checked whether it was possible to obtain a better agreement by adjusting the vertical cloud extinction within a reasonable range for stratus clouds (40 to 80 km −1 ). In a study presented by Lindberg et al (1984), profiles of the extinction within stratus clouds were obtained with lidar returns from ground based measurements and spectrometers and a point visibility meter carried aloft by a tethered balloon. Their extinction values within the stratus cloud vary between the aforementioned limits with a maximum extinction on the order of 100 km −1 .…”

Section: Surface Radiationmentioning

confidence: 99%

“…Their extinction values within the stratus cloud vary between the aforementioned limits with a maximum extinction on the order of 100 km −1 . Since we do not have measurements of the vertical extinction, it is reasonable to adjust this model parameter within the range observed by Lindberg et al (1984), in order to obtain a good agreement between model results and observation at the ground. In case a subsequent reasonable agreement is obtained between model results and satellite observations at TOA, we can conclude that the MODTRAN TM simulation of radiation transfer in the atmosphere including the cloud layer is satisfactory.…”

Section: Surface Radiationmentioning

confidence: 99%

Radiation transfer in stratus clouds at the BSRN Payerne site

Nowak

Vuilleumier

Ohmura

2008

Preprint

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Abstract. Clouds represent a major source of uncertainty in understanding climate change, because potential changes in the way they affect the atmospheric and surface energy budget are difficult to predict. It is therefore important to determine how clouds affect radiation. Stratiform clouds in particular have an important effect on climate as they cover large areas. This article presents results of radiation transfer calculations with MODTRANTM for well-defined stratus cloud cases detected at the meteorological station of Payerne, Switzerland. These stratus situations are selected in a data set covering the years from 2000 to 2005 with a method using data widely available at national meteorological observing stations. For 18 single layer stratus situations the shortwave radiation fluxes calculated with MODTRANTM are compared to surface observations from the Baseline Surface Radiation Network (BSRN) site at Payerne and top of atmosphere (TOA) observations from the Clouds and the Earth's Radiant Energy System (CERES) experiment. A median bias on the order of 20 Wm−2 (<9%) was found for the differences between modeled and observed reflected solar radiation at TOA. At the surface, good agreement is obtained by adjusting the vertical extinction in the modeled cloud layer within reasonable limits for a stratus cloud: The median bias of modeled minus observed shortwave downward radiation is well within instrument precision (<1%). The simultaneous agreement of modeled and observed radiation fluxes at the surface and TOA confirmed that radiation transfer in the atmosphere including a single cloud layer can be well simulated with MODTRANTM. Based on the present results, the absorbance was calculated within the stratus cloud layer (cloud base to cloud top). For the 18 single stratus layer situations the median absorbance is 0.07 [minimum 0.04, maximum 0.1], the median transmittance is 0.29 [0.15 0.39], and the median cloud reflectance is 0.70 [0.63, 0.80].

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“…We now consider the actual retrieval of cloud extinction coefficient for three different cloud typesstratocumulus, midlevel, and high cirrus clouds. Retrieval of extinction in stratocumulus was first considered by Lindberg et al (1984) and Carnuth and Reiter (1986). They both utilized the fact that the Klett backward integration converges to accurate values of afor some distance above cloud base for quite a wide range of values of o m (e.g., see Table 4).…”

Section: Stratocumulus Cloudsmentioning

confidence: 99%

The Experimental Cloud Lidar Pilot Study (ECLIPS) for Cloud—Radiation Research

Platt¹,

Young²,

Carswell³

et al. 1994

Bull. Amer. Meteor. Soc.

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The Experimental Cloud Lidar Pilot Study (ECLIPS) was initiated to obtain statistics on cloud-base height, extinction, optical depth, cloud brokenness, and surface fluxes. Two observational phases have taken place, in October-December 1989 and April-July 1991, with intensive 30-day periods being selected within the two time intervals. Data are being archived at NASA Langley Research Center and, once there, are readily available to the international scientific community. This article describes the scale of the study in terms of its international involvement and in the range of data being recorded. Lidar observations of cloud height and backscatter coefficient have been taken from a number of ground-based stations spread around the globe. Solar shortwave and infrared longwave fluxes and infra-red beam radiance have been measured at the surface wherever possible. The observations have been tailored to occur around the overpass times of the NOAA weather satellites. This article describes in some detail the various retrieval methods used to obtain results on cloud-base height, extinction coefficient, and infrared emittance, paying particular attention to the uncertainties involved. The above methods are then illustrated by both model simulations and by selected results from various laboratories. The ECLIPS data are shown to represent a valuable resource for cloud parameter-izations in models and for model validations.

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Lidar determinations of extinction in stratus clouds

Cited by 13 publications

References 1 publication

Ground-based retrieval of continental and marine warm cloud microphysics

Ground-based retrieval of continental and marine warm cloud microphysics

Radiation transfer in stratus clouds at the BSRN Payerne site

The Experimental Cloud Lidar Pilot Study (ECLIPS) for Cloud—Radiation Research

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