No abstract

The MAGICC (Model for the Assessment of Greenhouse gas Induced Climate Change) model simulation has been carried out for the 2000-2100 period to investigate the impacts of future Indian greenhouse gas emission scenarios on the atmospheric concentrations of carbon dioxide, methane and nitrous oxide besides other parameters like radiative forcing and temperature. For this purpose, the default global GHG (Greenhouse Gases) inventory was modified by incorporation of Indian GHG emission inventories which have been developed using three different approaches namely (a) Business-As-Usual (BAU) approach, (b) Best Case Scenario (BCS) approach and (c) Economy approach (involving the country's GDP). The model outputs obtained using these modified GHG inventories are compared with various default model scenarios such as A1B, A2, B1, B2 scenarios of AIM (Asia-Pacific Integrated Model) and P50 scenario (median of 35 scenarios given in MAGICC). The differences in the range of output values for the default case scenarios (i.e., using the GHG inventories built into the model) vis-à-vis modified approach which incorporated India-specific emission inventories for AIM and P50 are quite appreciable for most of the modeled parameters. A reduction of 7% and 9% in global carbon dioxide (CO 2 ) emissions has been observed respectively for the years 2050 and 2100. Global methane (CH 4 ) and global nitrous oxide (N 2 O) emissions indicate a reduction of 13% and 15% respectively for 2100. Correspondingly, global concentrations of CO 2 , CH 4 and N 2 O are estimated to reduce by about 4%, 4% and 1% respectively. Radiative forcing of CO 2 , CH 4 and N 2 O indicate reductions of 6%, 14% and 4% respectively for the year 2100. Global annual mean temperature change (incorporating aerosol effects) gets reduced by 4% in 2100. Global annual mean temperature change reduces by 5% in 2100 when aerosol effects have been excluded. In addition to the above, the Indian contributions in global CO 2 , CH 4 and N 2 O emissions have also been assessed by India Excluded (IE) scenario. Indian contribution in global CO 2 emissions was observed in the range of 10%-26%, 6%-36% and 10%-38% respectively for BCS, Economy and BAU approaches, for the years 2020, 2050 and 2100 for P50, A1B-AIM, A2-AIM, B1-AIM & B2-AIM scenarios. CH 4 and N 2 O emissions indicate about 4%-10% and 2%-3% contributions respectively in the global CH 4 and N 2 O emissions for the years 2020, 2050 and 2100. These Indian GHG emissions have significant influence on global GHG concentrations and consequently on climate parameters like RF and ΔT. The study reflects not only the importance of Indian emissions in the global context but also underlines the need of incorporation of country specific GHG emissions in modeling to reduce uncertainties in simulation of climate change parameters.

The energy balance equation for a general solar atmosphere without assuming the planeparallel approximation is solved analytically. This leads to models for both the transition region and inner corona as well as for the outer corona. The form of the latter is very similar to that of the hydrostatic conduction model of Chapman (1957). However, in this paper we confine ourselves only to the former.Model I is electron-pressure dependent but model II depends particularly on the maximum coronal temperature T,~ and its corresponding altitude h,M. Both the models are compared with recently constructed temperature models of Chiuderi and Riani (1974), McWhirter et al. (1975), and Gabriel (1976a. It is concluded that our model II reproduces these models within a factor of not more than 2.

We have performed self-consistent calculations to estimate the physical parameters of photodissociation regions (PDRs) associated with objects, namely, NGC 2024, Orion A and W3, using far-infrared continuum emission, fine-structure lines of C ii and O i, and radio recombination lines of carbon. Typically, PDRs separate H ii regions from the molecular cloud; therefore, necessary corrections for the contribution to C ii line emission due to the H ii region are made. For that purpose, using observational data, theoretical calculations are performed to obtain the best fit for the said observations. Three parameters, angular size, θ (in arcminutes), far-ultraviolet radiation field G0, and hydrogen density nH (which gives electron density and temperature), are varied, and the sets of parameters (G0 and nH) obtained for the NGC 2024, Orion A and W3 PDRs are (7.6 × 104 and 1.2 × 105 cm−3), (2.8 × 105 and 2.3 × 105 cm−3) and (3.7 × 105 and 1.9 × 105 cm−3), respectively. The relationship between line and continuum emissions from PDRs associated with H ii regions leads us to conclude that exciting stars for the NGC 2024, Orion A and W3 H ii regions are O8–O9V, O6–O7V and O5–O6V, respectively.

No abstract