Relative humidity impact on aerosol parameters in a Paris suburban area

Measurements of relative humidity (RH) and aerosol parameters (scattering cross section, size distributions and chemical composition), performed in ambient atmospheric conditions, have been used to study the influence of relative humidity on aerosol properties. The data were acquired in a suburban area south of Paris, between 18 and 24 July 2000, in the framework of the 'Etude et Simulation de la Qualit&#233; de l'air en Ile-de-France' (ESQUIF) program. According to the origin of the air masses arriving over the Paris area, the aerosol hygroscopicity is more or less pronounced. The aerosol chemical composition data were used as input of a thermodynamic model to simulate the variation of the aerosol water mass content with ambient <i>RH</i> and to determine the main inorganic salt compounds. The coupling of observations and modelling reveals the presence of deliquescence processes with hysteresis phenomenon in the hygroscopic growth cycle. Based on the H&#228;nel model, parameterisations of the scattering cross section, the modal radius of the accumulation mode of the size distribution and the aerosol water mass content, as a function of increasing RH, have been assessed. For the first time, a crosscheck of these parameterisations has been performed and shows that the hygroscopic behaviour of the accumulation mode can be coherently characterized by combined optical, size distribution and chemical measurements

Pregnancy-related pelvic girdle pain: an update

A large number of scientists from a wide range of medical and surgical disciplines have reported on the existence and characteristics of the clinical syndrome of pelvic girdle pain during or after pregnancy. This syndrome refers to a musculoskeletal type of persistent pain localised at the anterior and/or posterior aspect of the pelvic ring. The pain may radiate across the hip joint and the thigh bones. The symptoms may begin either during the first trimester of pregnancy, at labour or even during the postpartum period. The physiological processes characterising this clinical entity remain obscure. In this review, the definition and epidemiology, as well as a proposed diagnostic algorithm and treatment options, are presented. Ongoing research is desirable to establish clear management strategies that are based on the pathophysiologic mechanisms responsible for the escalation of the syndrome's symptoms to a fraction of the population of pregnant women

Retrieving the aerosol single-scattering albedo from the NO2 photolysis rate coefficient

International audienceA method for retrieving the aerosol single-scattering albedo ω0 in the ultraviolet region close to 400 nm within the atmospheric column is proposed based on a comparison between both NO2 photolysis rate coefficients JNO2 measured by an optical actinometer under cloud-free conditions and JNO2 calculated using a radiative transfer model. This methodology is based on the sensitivity of JNO2 to ω0 variations as quantified using the radiative transfer model with particular emphasis on the aerosol extinction vertical profile. The method has been applied to assess ω0 within the framework of the Indian Ocean Experiment (INDOEX) over the Goa area located on the west coast of India. In the first place, the period under study was between March 2 and March 13, 1999 when ground-based lidar measurements were available. It has been further extended between February 25 and March 23, 1999 by making appropriate assumptions on the mean altitude of the aerosol layer. Taking into account the uncertainties related to each parameter introduced in the calculation (optical thickness, Ångstróm coefficient, asymmetry factor, surface albedo) and the model used, resulted in a total absolute accuracy on ω0 calculated to be 0.06 for observations close to local noon, and up to 0.07 for observations performed within 3 h before and after local noon. Results are less accurate for other times. For the 12 days under study, the values of ω0 calculated at noon range from 0.89 to 0.93. They vary weakly throughout the day with further differences being observed from one day to another. Such small variations in ω0 are in very good agreement with results obtained by other methods within the framework of the same campaign

Relative humidity impact on aerosol parameters in a Paris suburban area

International audienceMeasurements of relative humidity (RH) and aerosol parameters (scattering cross section, size distributions and chemical composition), performed in ambient atmospheric conditions, have been used to study the influence of relative humidity on aerosol properties. The data were acquired in a suburban area south of Paris, between 18 and 24 July 2000, in the framework of the "Etude et Simulation de la Qualité de l'air en Ile-de-France" (ESQUIF) program. According to the origin of the air masses arriving over the Paris area, the aerosol hygroscopicity is more or less pronounced. The aerosol chemical composition data were used as input of a thermodynamic model to simulate the variation of the aerosol water mass content with ambient RH and to determine the main inorganic salt compounds. The coupling of observations and modelling reveals the presence of deliquescence processes with hysteresis phenomenon in the hygroscopic growth cycle. Based on the Hänel model, parameterisations of the scattering cross section, the modal radius of the accumulation mode of the size distribution and the aerosol water mass content, as a function of increasing RH, have been assessed. For the first time, a crosscheck of these parameterisations has been performed and shows that the hygroscopic behaviour of the accumulation mode can be coherently characterized by combined optical, size distribution and chemical measurements

Aerosol direct radiative impact over the INDOEX area based on passive and active remote sensing

International audienceThis study is dedicated to the direct radiative impact assessment of the pollution aerosol particles during the Indian Ocean Experiment (INDOEX). We use here an instrumental synergy based on active and passive ground‐based (Goa University, India), airborne (Mystere 20 research aircraft), and spaceborne (Meteosat‐5) devices. An original method based on ground‐based active actinic flux measurements is developed to assess the atmospheric, columnar aerosol single scattering albedo. This parameter has been found between 0.88 and 0.93 (at 440 nm) with an absolute uncertainty of 0.04 during the operating period from 11 to 23 March 1999. We have also assessed this parameter off the West Indian coast by comparing simultaneous airborne lidar and flux measurements with radiative transfer simulations. The value retrieved for the atmospheric column is close to 0.83 ± 0.05 (at 523 nm) in agreement with the coastal value. The horizontal and vertical extent of the aerosol plume is investigated using airborne lidar and Meteosat‐5 satellite. Using the Meteosat‐5‐derived aerosol optical thickness, we have estimated the regional extent of the shortwave aerosol direct radiative forcing. The vertical profile of the aerosol extinction coefficient derived from lidar sounding is used to assess the atmospheric shortwave heating rate induced by the aerosol layer. For an aerosol optical thickness of 0.6 (±0.12), as it has been observed in the aerosol plume in late March, the top of atmosphere direct aerosol forcing is −17 (±5) W m−2. The surface forcing is between 2.5 and 4.5 higher than the top of atmosphere forcing. This difference leads to a significant heating of the three lowest kilometers of the atmosphere by the aerosols. For an aerosol optical thickness of 0.6, the atmospheric heating rate induced by aerosols is between 0.8 and 1.2 Kd−1 depending on the aerosol single scattering albedo value