S. Ferrarese

Localization of source and sink regions of carbon dioxide through the method of the synoptic air trajectory statistics

Abstract The main purpose of this paper is to contribute to the improvement of the present knowledge concerning the transient components of the global carbon cycle, superimposed to the periodic seasonal oscillation and to the yearly trend. This purpose has been achieved through the comparison among the calculated concentration fields of atmospheric CO2 and its comparison with the sea-surface temperature patterns, forestation maps, forest fires, and the anthropogenic emissions extracted from Edgar V.2.0 database. In order to identify with high spatial resolution the most relevant areas of CO2 sources and sinks, we have applied a methodology based on a statistical analysis of simulated back-trajectories related to atmospheric concentration values measured at some receptor sites where the back-trajectories originate. In particular, we have used a 2-year time series (1996 and 1997) of CO2 concentration data observed in three receptor sites located in high mountain areas, in order to reduce significantly the effects due to local influences (such as emissions from industries and urban areas or the absorption processes due to the vegetation). The back-trajectories were computed by means of the wind fields provided by the ECMWF analysis (T213/L31 model) on a regular grid. The area investigated was from 11°W to 36°E in longitude and from 30°N to 57°N in latitude. The final concentration field was computed by means of a statistical source–receptor model, based on a methodology developed by Stohl (Atmos. Environ. 30 (1996) 579) and adapted here with some modifications in the pre- and post-processing phases. Before applying the model, a careful evaluation of its sensitivity to the input data has been performed, followed by an analysis to identify the optimal configuration of the model. The results have shown a satisfactory accuracy in the identification of the major sources and sinks considered.

Influence of the Sonic Anemometer Temperature Calibration on Turbulent Heat-Flux Measurements

The speed of sound in moist air is discussed and a more accurate value for the coefficient of the linear dependence of sonic temperature on specific humidity is proposed. An analysis of speed-of-sound data measured by three sonic anemometers in a climate chamber and in the field shows that the temperature response of each instrument significantly influences not only the determination of sonic temperature, but also its fluctuations. The corresponding relative contribution to the error in the evaluation of the temperature fluctuations and the turbulent heat fluxes can be as high as 40%. The calibration procedure is discussed and a method of correction is proposed.

A study of greenhouse gases and air trajectories at Plateau Rosa

SummaryThe attention paid to changes in atmospheric concentrations of greenhouse gases has recently increased, with particular regard to the relationships between variations of their annual trends and of their shorter-period fluctuations on the one hand, and some geophysical and biological natural processes (like atmospheric transport, volcanic eruptions, ENSO events, seasonal vegetation cycles, and so on) on the other hand. Careful analysis and interpretation of the above relationships, in fact, can often disclose unknown mechanisms acting on modulations of these gases and make it possible for us to better understand the contributions made to them by natural causes, contrasted with anthropogenic ones. This paper presents and discusses the results of a series of CO2 air concentration data, measured at Plateau Rosa (3480 m a.s.l.—Italian Western Alps) over a period of about four years, and correlated with atmospheric transport processes on synoptic scale. These results have shown the leading role played by some kinds of atmospheric circulation patterns in creating situations of not fully mixed air streams (and, as such, not representative of background conditions) and have also suggested a «meteorological» selection scheme for CO2 data to be used in evaluating more reliable annual trends.

Inspection of high-concentration CO2 events at the Plateau Rosa Alpine station

The Plateau Rosa Alpine station (Italy) has collected atmospheric concentrations of carbon dioxide since 1989. If the complete set of hourly data is observed, two distinct and exceptional very high concentration events are evident for February 2004. Similar and almost contemporary peaks were registered at the European high–altitude stations of Zugspitze–Schneefernerhaus and Sonnblick in the Alps, and at Mt. Cimone in the Northern Apennines. A regional meteorological model (the Weather Research and Forecast) was applied over a medium–high resolution grid to study the evolution of the meteorological fields and to identify the trajectories of the polluted air masses during the CO2 observed peaks. The results show that, during both episodes, atmospheric circulation conveyed highly polluted air from the European plains to the Alpine stations. This conclusion has been also confirmed through concentration measurements of the atmospheric trace gases in the same area.

Identification, tracking, validation and forecast of local high resolution precipitation patterns observed through X-band micro radars

In this paper, the application of a weather radar software for storm identification, tracking and forecast to a short range X-band rain radar observations is presented. Preliminary results are given, applying such tool to high space-time resolution both convective and stratiform precipitation scenarios. Good qualitative and quantitative agreement are observed. Moreover, for the first time, rain derived observations performed by such small radars were compared with independent data. Both high resolution numerical weather forecast models simulations and true observations taken by collocated rain gauges are considered. Good qualitative agreements for both cases are obtained.