Trends in Global Marine Cloudiness and Anthropogenic Sulfur

Parungo, F.; Boatman, Joe F.; Sievering, H.; Wilkison, Stan W.; Hicks, B. B.

doi:10.1175/1520-0442(1994)007<0434:tigmca>2.0.co;2

Cited by 36 publications

(26 citation statements)

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“…Hence, more significant levels will be selected. The findings in our paper are consistent with other studies (see Dai et al 1997;Easterling et al 1997;Henderson-Sellars 1992;Karl and Steuer 1990;London et al 1991;Parungo et al 1994). …”

Section: Fig I Cloud Layers Determined By the Ce Methods Forsupporting

confidence: 94%

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Seidel¹,

Durre²

2003

Bull. Amer. Meteor. Soc.

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C hernykh et al. (2001, hereafter CAE) report trends in cloud-base height, cloud-top height, the number of cloud layers, and the frequency of clouds based on analysis of global radiosonde data during 1964-98. We are concerned that the changing vertical resolution of radiosonde observations over time, combined with the sensitivity of the method used to deduce cloud layers (Chernykh and Eskridge 1996, hereafter CE) to vertical resolution, undermine the credibility of the reported trends. This comment provides evidence both that the CE method is very sensitive to vertical resolution, and that the vertical resolution of soundings has increased over the past four decades. From this evidence we argue that the reported trends are, at least in part, artifacts of changing observing practices. We also raise other questions regarding the influence of data sampling on the results.The CE method for determining cloud layers from radiosonde temperature and humidity profiles involves identifying vertical layers in which the second derivative of temperature with respect to height is zero or positive, and the second derivative of relative humidity with respect to height is zero or negative. The endpoints of layers meeting these criteria are interpreted as cloud bases and tops. CAE apply this DOI: 10.1 I75/BAMS-84-2-237 AMERICAN METEOROLOGICAL SOCIETY method to data from 967 radiosonde stations and report a globally averaged increase in cloud-top height of about 154 m decade -1 , a decrease in cloud-base height of about 44 m decade -1 , a 1.7% decade -1 increase in the frequency of clouds, and an unquantified increase in the frequency of multilayer clouds.Given the implications of these findings for interpreting other changes in climate, it is important to determine whether they are robust. Changes in instruments and observing practices are manifest in time series of radiosonde temperature (Gaffen 1994; Parker and Cox 1995) and humidity (Elliott and Gaffen 1991) records and, if not accounted for, can severely undermine attempts to estimate temperature trends (Gaffen et al. 2000). Since the CE method infers cloud layers from temperature and humidity profiles, it is reasonable to question whether temporal data inhomogeneities also impact radiosondederived cloud trends. SENSITIVITY OF CUBIC SPLINE INTERPO-LATION TO DATA RESOLUTION.Radio sonde data are reported at discrete pressure levels, resulting in a piecewise linear vertical profile. However, because piecewise linear functions have discontinuous first derivatives, the CE method involves fitting a cubic spline to sounding data to allow evaluation of the second derivatives of temperature and humidity with the respect to height. As an aside, we note that spline fits are contradictory to the reporting requirements for radiosonde data, which stipulate that a data level be reported when the soundings departs significantly from a linear fit between reported levels (Hooper 1986; WMO 1996; OFCM 1997). Although it seems likely that atmospheric profiles have continuous second derivatives...

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Section: Fig I Cloud Layers Determined By the Ce Methods Forsupporting

confidence: 94%

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Seidel¹,

Durre²

2003

Bull. Amer. Meteor. Soc.

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“…Long-term upward trends in altostratus and nimbostratus clouds are reported for the mid-latitude North Pacific and North Atlantic Oceans [93]. For the years from 1952 to 1995 an increase in total sky cover of about 2% and an increase of about 4% in low cloud cover is found [94].…”

Section: Observed Changes In Cloudinessmentioning

confidence: 94%

The role of clouds in the climate system

Quante¹

2004

J. Phys. IV France

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Abstract. Clouds are important for global climate since they have a strong impact on solar and terrestrial radiation as well as on the formation of precipitation. The different types of clouds in the atmosphere are linked to the climate system by a multitude of dynamical and thermodynamical processes including numerous feedback mechanisms. In present-day climate, on average, clouds cool our planet, the net cloud radiative forcing at the top of the atmosphere is about -20 Wm -2 . One of the most interesting questions concerning clouds is: how will they respond to a change in climate? A slight change in cloud amount or a shift in the vertical distribution of clouds might have a considerable impact on the energy budget of the Earth. The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states clearly that cloud processes and related feedbacks are among the physical processes leading to large uncertainties in the prediction of future climate. The main reason for this is that many microphysical and dynamical processes controlling the life cycle and radiative properties of clouds are not adequately implemented in global climate models. The interaction of aerosols and clouds and the resulting radiative forcing (indirect and semidirect aerosol effect) is one of the major fields of active cloud research at present. This chapter introduces various aspects of the cloud-climate relation and summarizes the discussions of topics currently under scientific debate.

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“…During this event, new particles evidently were formed due to specific reactions, which occur over the sea at night, involving organic compounds [9]. It may be supposed that primary BC is emitted to the atmosphere as hydrophobic particles, eventually becoming hydrophilic by oxidation or after coating by soluble aerosols such as sulphate and organics [27]. Consequently, at wavelengths of 370 nm, certain kinds of organic compounds start to show strong UV absorption [28].…”

Section: Particle Size Distribution and Bcmentioning

confidence: 99%

Black carbon aerosol at the background site in the coastal zone of the Baltic Sea

Andriejauskienė¹

2008

Lithuanian J. Phys.

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Carbon particulate matter constitutes an important portion of the atmospheric aerosol and directly participates in the formation of the Earth's radiation balance by influencing the global and regional climate. Continuous data (March, April, 2002) of 20-minute concentrations of airborne black carbon (BC) particles at the Preila Environmental Pollution Research Station (55• 20 N, 21• 00 E) have been used for the investigation of diurnal and weekday variation as well as the different air mass influence on BC transport. The measurement of BC mass concentration with the Aethalometer TM , Model AE40 Spectrum, manufactured by Optotek, Slovenia was carried out. The origin of an air mass was detected by using air mass backward trajectories calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectories (HYSPLIT) model. Approximately 73% of BC measured concentrations were found in the range of a low value mode centered at ∼0-1000 ng m −3 . The remaining concentrations were in a high-concentration mode at ∼1000-3000 ng m −3 , probably indicating a direct impact of emissions from combustion activities. BC concentration in various air masses over that period varied from the average value of approximately 140 ng m −3 to the maximum value of 2410 ng m −3 . The highest BC concentrations were associated with the prevailing southern transport air masses. Simultaneously, the daily concentration variation of black carbon and SO2, NO2, O3 was measured and analysed. Total aerosol concentrations and size distributions were measured as well. The aerosol size distribution was plotted as contour plots for each day (as a function of time). Most studies were focused on the BC aerosol particle size distribution and modal aerosol concentration. For each event, the growth rate was calculated graphically from the contour plots ("banana-plots") and was analysed for the possible nucleation events. Some aerosol measurements were carried out at an urban site in order to evaluate the BC concentration of the freshly emitted traffic aerosols.

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Trends in Global Marine Cloudiness and Anthropogenic Sulfur

Cited by 36 publications

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The role of clouds in the climate system

Black carbon aerosol at the background site in the coastal zone of the Baltic Sea

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