Simulations of airglow variations induced by the CO2 increase and solar cycle variation from 1980 to 1991

Abstract

Airglow intensity and Volume Emission Rate (VER) variations induced by the increase of CO2 gas concentration and F10.7 variation (used as a proxy for the 11-year solar cycle variation) were investigated for the period of 1980 to 1991, encompassing a full solar cycle. Two airglow models are used to simulate the induced variations of O(1 S) greenline, O2(0,1) atmospheric band , and OH(8,3) airglow for this study. The results show that both the airglow intensities and peak VERs correlate positively with the F10.7 solar cycle variation and display a small linear trend due to the increase of CO2 gas concentration. The solar-cycle induced airglow intensity variations show that O(1 S) greenline has the largest variation (~26%) followed by the O2(0,1) atmospheric band (~23%) and then OH(8,3) airglow (~8%) over the 11 year timespan. The magnitudes of the induced airglow intensity variations by the increase of CO2 gas concentration are about an order of magnitude smaller than those by the F10.7 solar cycle variation. In general, the F10.7 solar cycle variation and CO2 increase do not seem to systematically alter the VER peak altitude of the airglow emissions, though the OH(8,3) VER peak altitude moves up slightly during the years when the F10.7 value falls under 100 SFU.

Trends in the Airglow Temperatures in the MLT Region—Part 1: Model Simulations

“…That we need to quantitatively assess the variations of airglow intensities and temperatures by the known influences was the motivation for the current study and previous numerical studies by [8][9][10]. As pointed out in [8], the advantage of a numerical approach is that we can do controlled simulations to better assess the individual impact of the influences.…”

“…That we need to quantitatively assess the variations of airglow intensities and temperatures by the known influences was the motivation for the current study and previous numerical studies by [8][9][10]. As pointed out in [8], the advantage of a numerical approach is that we can do controlled simulations to better assess the individual impact of the influences. The author of [9] did a simulation study to investigate how airglow intensities and Volume Emission Rates (VERs) would change in response to hypothetical scenarios of CO 2 doubling, CO 2 decreased by half and CO 2 increased by 10%.…”

“…As shown in [7], airglow is very sensitive to global change, which is not surprising, because airglow is known to be sensitive to atmospheric conditions. However, as pointed it out by [8], "using airglow measurements to deduce the change by the increase of anthropogenic gas emissions presents some challenges . .…”

Trends in the Airglow Temperatures in the MLT Region—Part 3: Ground-Based and SABER Measurements

“…Instead of finding a linear trend directly from the dataset, we decided to use a different approach. It is known from simulation studies that an increase of CO 2 gas concentration in the lower atmosphere leads to cooling in the upper atmosphere [6,7,[18][19][20]. With a long-term record of CO 2 gas emission data, the simulations in [7] showed that the temperature in the airglow altitudes would decrease at a rate of~0.05 K/year in response to the increase of CO 2 gas concentration.…”

Trends in the Airglow Temperatures in the MLT Region—Part 2: SABER Observations and Comparisons to Model Simulations

“…These studies have focused on finding a linear trend or a solar trend using F10.7 as a proxy for solar cycle variation, since the solar radio flux at 10.7 cm (2800 MHz) is an excellent indicator of solar activity. The recent simulation studies by the authors of [7,8] showed that airglow intensities of OH (8,3), O 2 atmospheric band, and O( 1 S) Greenline in the Mesosphere and Lower Thermosphere (MLT) region responded to the influences of the CO 2 increase and the F10.7 and Ap index variations. In these studies, OH Chemistry Dynamics (OHCD) and Multiple-Airglow Chemistry Dynamics (MACD) airglow models [9][10][11][12] were used to simulate airglow response to the influences.…”