Andrey A. Kiselev

Global warming potential, global warming commitment and other indexes as characteristics of the effects of greenhouse gases on Earth’s climate

Abstract Radiative forcing (RF) is widely used for evaluation of separate radiative active substance effects on climate. For photochemically active greenhouse gases, this effect detachment for the definite radiative active substance content change poses the problem of filtering out of all other chemically connected greenhouse gas effects. Two schemes of RF calculation for such greenhouse gas are proposed and analyzed: the cumulative and the individual ones as the direct generalization of the standard RF definition and the filtering out procedure, respectively. The global warming commitment (GWC) of gas X relative to a standard gas A for time period T is proposed and determined by the same formula, as the well-known global warming potential (GWP) of gas X , but for different integrated radiative forcing (RF). RF X ( t )=Δ F X ( t ) is the net total radiation flux change at the tropopause level caused only by a gas X content variation during the period of integration. In the GWP of a gas X , Δ F X ( t ) and Δ F A ( t ) appear due to instantaneous releases into the atmosphere of the same definite mass (1xa0kg) of gas X and of a standard gas A . In the GWC, the actually measured or modeled gas content evaluations are used for the estimation of gas X relative input into the current and future greenhouse warming. The GWC of the principal greenhouse gases (GG) are calculated and analyzed for the period before 1995, calculations and analysis being based on the observed GG content evolution. For this period and for the period from now until 2050, the global GG content evolution reconstruction and prediction by means of radiative photochemical atmospheric model are based on two of the well-known IPCC scenarios of GG anthropogenic emissions. The GWCs of CH 4 , N 2 O and chlorofluorocarbons (CFCs) against CO 2 as a standard GG are different from their relative RF and much more accurately reflect the real events in the above mentioned periods than the widely used RF of GG relative to RF of CO 2 , when the character of the GG content evolution during the time period considered is not accounted for. The filtering efficiency of cumulative and individual schemes is estimated.

Plume transformation index (PTI) of the subsonic aircraft exhausts and their dependence on the external conditions

A concept of the PTI is proposed to characterize the photochemical interactions of aircraft exhausts with the ambient air. The PTI is the ratio of NOx, CO,, ozone, and NOy transformed in the plume during its lifetime period tp to NOx and CO released into the plume initially. An estimate of tp is calculated by prescribing the 10% excess of emitted (NOx)p in the plume over the (NOx)a of the ambient air at the end of plume life. Simple analytical formulas for PTI are obtained from the known plume box model. The tp, PTI of NOx, HNO3 and O3 are calculated and analyzed for different moments of releases during the daytime in and out of flight corridor. The in-plume NOx conversion to HNO3 and O3 enhancement are found to be the largest in daytime, in July and in the lower stratosphere.

Modeling of the long-term tropospheric trends of hydroxyl radical for the Northern Hemisphere

Abstract The MGO 2D (altitude–longitude) channel photochemical transport model has been applied to elucidate the spatial and temporal behavior of the hydroxyl radical in the troposphere of the northern temperate belt for the pre-industrial (1850) period and the last few decades (1960 and 1995). The relation between the tropospheric OH content and the carbon monoxide, methane, nitrogen oxides emissions during 1850–1995 is studied. The distribution of the carbon monoxide concentration is calculated and validated using the observational data collected in the different locations because of the geographical non-homogeneity of its emissions. The response of the hydroxyl radical concentrations to the non-homogeneity of the CO and other atmospheric species distribution is estimated. The carbon monoxide and methane contributions to the hydroxyl photochemical sink are also evaluated. Because the changes of OH in the troposphere alternate the intensity of methane and carbon monoxide oxidation, the CO, CH4 and OH lifetime evolution due to the increase of anthropogenic pollution intensity is analyzed and discussed.

Model study of tropospheric composition response to NOx and CO pollution

Abstract The effect of NO x and CO pollution on other important atmospheric gases from 0–16 km in the northern temperate zonal belt is calculated using a 2-D (altitude–longitude) channel photochemical model with climatic zonal and vertical fixed transport. The geographical inhomogeneities of the NO x and CO large-scale surface releases are modeled. The distinction between NO x and CO fluxes from the oceanic and land surfaces and those from areas with various pollution source intensities is considered. NO x and CO emissions from world transport aviation engine exhausts and the NO source from lightning discharges are also included. Model results are analyzed and compared with observational data for nitrogen compounds, carbon monoxide, and ozone. The dependence of the spatial and temporal hydroxyl distribution on the carbon monoxide (as the main destroyer of OH) concentration field is analyzed and discussed.

The ratio between nitrogen oxides and carbon monoxide total emissions as precursors of tropospheric hydroxyl content evolution

Abstract The Main Geophysical Observatory 2D channel photochemical model is used to study the behavior of tropospheric OH within the 30–60°N zonal belt in relation to changing NOX and CO emissions. The changes of tropospheric OH as a function of the contributions by NOX and CO emissions during the period 1850–2050 are calculated. Our estimations show that the largest annual increment of total tropospheric OH within the belt considered occurs in the 1985–1995 period, about 0.27% yr −1 . Based on scenarios of tropospheric pollution emissions in the first half of 21st century, the total tropospheric OH content will increase more slowly, by 0.12– 0.15% yr −1 . The maximum growth of OH concentration occurs close to air pollution locations—in the lower troposphere during 1850–1995 but in the upper troposphere in the 21st century when the NOX source from subsonic aircraft increases faster than the surface source.

The Dependence of Tropospheric Hydroxyl Content on the Alignment Between the NOx and CO Total Emissions

Many theoretical studies testify to an exceptionally important role of OH radical in the tropospheric chemistry (Crutzen, Zimmermann, 1991; WMO/UNEP, 1999; etc.). Due to its extremely high reactivity, OH controls or essentially influences the content of many tropospheric species, such as carbon monoxide CO, methane CH4, ozone O3, nitrogen oxides and others. Simultaneously, these species determine the behavior of tropospheric OH. As a result of their chemical interactions, the quantitative estimations of tropospheric hydroxyl concentration were calculated by the models of different complexity (e.g. Lelieveld et al., 1998; Wang, Jacob, 1998; Kiselev, Karol, 1999, 2000a). But it is difficult to validate them by the relevant observations, as there is presently no instrumentation for regional to global scale those of tropospheric OH (Brasseur, Prinn, 2000). Thus, the regular monitoring of tropospheric OH is not yet established and there are a few its isolated measurements only (e.g. Kleinman et al., 1998; Brune et al., 1999). Under the circumstances modeling is a basic tool of study of tropospheric OH chemistry. Up to now there is no common opinion among the specialists about the evolution of tropospheric OH, and the modern model reconstructions of its trend differ not only in magnitude but in sign. According to Martinerie et al. (1995), Kiselev, Karol (2000a) the tropospheric OH content has been increasing last 150 years but other studies (e.g. Lelieveld et al. (1998), Chappellaz et al. (1993)) evaluate the drop of tropospheric OH in the same period.

Global Warming Potential and Global Warming Commitment Concepts in the Assessment of Climate Radiative Forcing Effects

The Global Warming Potential (GWP) and Radiative Forcing (RF) are widely used for the evaluation a separate Radiative Active Substance (RAS) effects on the climatic regime of the atmosphere. In a radiative photochemical model, calculations of RF of the chemically active Greenhouse Gases (GG) caused by gas content change is proposed in two ways: by the Cumulative (CS) and Individual (IS) schemes. The Global Warming Commitment (GWC) is calculated by the same formula as GWP, but considering actual RAS emission and RAS content changes in certain periods. GWC specifies the RF of RAS by taking into account not only the initial and final RAS concentration distribution as RF does, but also the concentration evolution during the period. All these indices are calculated and analysed for periods: 1850–1995 and 1995–2050 for two IPCC IS92 scenarios.

Effective Emission Indices (EEI) of the Subsonic Air Transport Exhausts and Estimations of their World Inventories

A concept of Effective Emission Indices (EEI) was introduced by several authors to assess the effects of photochemical processes in the exhaust plume on the exhaust product global inventory. We divide EEI in two factors: EEI = EI × PTI, where the known Emission Index (EI) quantifies the in-engine processes and dimensionless Plume Transformation Index (PTI) is the ratio of the NOX, NOY components, O3 or CO molecules transformed in the plume during its lifetime period to the initially emitted NOX or CO molecules into the plume. The plume lifetime period is limited by setting the prescribed small excess (10%) of emitted (NOX)P in the plume over the (NOX)a of the ambient air. EI is estimated for the most of currently used aircraft engines (IPCC, 1999). PTI was calculated by Meijer et al. (1997) and Karol et al. (1999) using the plume photochemical model for various ambient conditions.