Specified dynamics scheme impacts on wave-mean flow dynamics, convection, and tracer transport in CESM2 (WACCM6)

Specified dynamics schemes are ubiquitous modeling tools for isolating the role of dynamics and transport on chemical weather and climate. They typically constrain the circulation of a chemistry-climate model to the circulation in a reanalysis product through linear relaxation. However, recent studies suggest that these schemes create a divergence in chemical climate and the meridional circulation between models and do not accurately reproduce trends in the circulation. In this study we perform a systematic assessment of the specified dynamics scheme in the Community Earth System Model version 2, Whole Atmosphere Community Climate Model version 6 (CESM2 (WACCM6)), which proactively nudges the circulation toward the reference meteorology. Specified dynamics experiments are performed over a wide range of nudging timescales and reference meteorology frequencies, with the model's circulation nudged to its own free-running output - a clean test of the specified dynamics scheme. Errors in the circulation scale robustly and inversely with meteorology frequency, and have little dependence on nudging timescale. However, the circulation strength and errors in tracers, tracer transport, and convective mass flux scale robustly and inversely with nudging timescale. A 12 to 24 hour nudging timescale at the highest possible reference meteorology frequency minimizes errors in tracers, clouds, and the circulation, even up to the practical limit of one reference meteorology update every timestep. The residual circulation and eddy mixing integrate tracer errors and accumulate them at the end of their characteristic transport pathways, leading to elevated error in the upper troposphere/lower stratosphere and in the polar stratosphere. Even in the most ideal case, there are non-negligible errors in tracers introduced by the nudging scheme. Future development of more sophisticated nudging schemes may be necessary for further progress.

An Empirical Approach toward the SLCF reduction targets in Asia for the Mid-term Climate Change Mitigation

Although importance of co-control of SLCFs together with the emission reduction of CO 2 has attracted much attention for the mid-term climate change mitigation, their contribution to radiative forcing (RF) are rather complex, and chemical-climate model analysis for the future scenario tends to give black box for the contribution of each species. In order to deliver a more straightforward message on the effect of the reduction of SLCFs to policymakers, we propose “top-down” reduction targets of CH 4 and tropospheric O 3 in reference to the historical levels of their RF. Although the RF increase due to the increasing CO 2 concentration is inevitable in mid-term future (ca. 0.80 W m -2 in 2040), the RF of CH 4 and O 3 is expected to decrease from 0.48 to 0.41, 0.34, 0.27, and 0.22 W m -2 , and from 0.40 to 0.29, 0.23, 0.19, and 0.15 W m -2 , respectively, if their atmospheric concentrations decrease from the level of 2010 to those of 1980, 1970, 1960 and 1950, according to the IPCC 2013 database. Consequently, the sum of -ΔRF x (CH 4 ) and -ΔRF x (O 3 ) (the difference of RF between the target year of x and 2010 as the base year) are 0.18, 0.31, 0.42 and 0.51 W m -2 in 1980, 1970, 1960 and 1950, respectively. This indicates that the increase of ΔRF 2040 (CO 2 ) can be compensated by of 23 to 64%, and the policy target can be selected from the combination of different target years for CH 4 and O 3 . With these global reduction ratio the necessary reductions in CH 4 , NO x, and NMVOC in Asia was estimated and compared with the GAINS model-based cost-beneficial reduction amount proposed by the Solution Report prepared under UN Environment Asia pacific Office. The comparison suggests that the reduction of O 3 to the 1970 level is promising if the emissions of NO x and NMVOC from other parts of the world are reduced coherently, but further efforts would be necessary for the reduction of CH 4 emissions to realize the 1970 concentration level.

The forecast of erythemal UV irradiance over the territory of Northern Eurasia according to the INM-RSHU chemical-climate model

In this work, the impact of various factors on the total ozone column and erythemal UV radiation (Qery) in the territory of Northern Eurasia for the period from 1979 to 2059 based on the calculations of the chemical-climate model INM-RHSU is analyzed. The sensitivity of ozone recovery to the setting of different input data on sea surface temperature (SST) is estimated. Depending on the SST datasets, there are significant differences in ozone trends. A possible mechanism that explains the reasons for these differences is examined. The numerical experiment with the only change in ozone depleting substances according to Montreal protocol showed the ozone recovery and, as a result, Qery reduction, but this recovery is not linear. During the 2016-2020 period we estimated the 2-5% increase in Qery values relative to the baseline period (1979-1983) with about 6% maximum over Russian polar region. During the 2035-2039 period the Qery change against 1979-1983 period is about zero, during the 2055-2059 period we obtained the decrease of about 4-6% over Northern Asia and 6-8% over Northern Europe These changes corresponded to the noticeable boundary location shift of UV resources, which determine UV radiation impact on human health. The most significant changes will be observed in spring and summer: the UV deficiency zone will be expanded in the north and the UV excess zone over northern seas will be reduced in the south.

Variations in snow and firn chemistry along US ITASE traverses and the effect of surface glazing

This study provides a baseline from which changes in the chemistry of the atmosphere over Antarctica can be monitored under expected warming scenarios and continued intensification of industrial activities in the Southern Hemisphere. It is the first study to measure more than 25 chemical constituents in the surface snow and firn across extensive regions of Antarctica. We present major ion, trace element, heavy metal, rare earth element and oxygen isotope data from a series of surface snow samples and shallow firn sections collected along four US ITASE traverses across East and West Antarctica. In each sample we measure dissolved concentrations of Na+, K+, Mg2+, Ca2+, Cl−, NO3+, SO42−, and MS− using ion chromatography and total concentrations of Sr, Cd, Cs, Ba, La, Ce, Pr, Pb, Bi, U, As, Al, S, Ca, Ti, V, Cr, Mn, Fe, Co, Na, Mg, Li, and K using inductively coupled plasma sector field mass spectrometry (ICP-SFMS). We also measure δ18O by isotope ratio mass spectrometry. Satellite remote sensing measurements of microwave backscatter and grain size are used to assist in the identification of glaze/dune areas across Antarctica and determine if these areas can possibly contain useful chemical climate records. The majority of the non-glaze/dune samples in this study exhibit similar, or lower, concentrations to those from previous studies. Consequently, the results presented here comprise a conservative baseline for Antarctic surface snow chemical concentrations. The elements Cd, Pb, As and Bi are enriched across Antarctica relative to both ocean and upper crust elemental ratios. Local and global volcanic outgassing may account for the majority of the Bi measured in East and West Antarctica and for a significant fraction of the Cd and As. However, significant concentrations of Cd, Pb, and As remain across much of Antarctica.

Kjemisk klima og helseproblemer

<strong><span style="font-family: TimesNewRomanPS-BoldMT;"><span style="font-family: TimesNewRomanPS-BoldMT;"><p align="left"> </p></span></span><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;"><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;">SAMMENDRAG</span></span></strong><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><p align="left">Fysiske klimafaktorer har alltid vært fulgt med oppmerksomhet fra menneskene, mens interessen for</p><p align="left">kjemisk klima er av nyere dato. Viktige årsaker til den nye interessen er at naturforurensning tillegges</p><p align="left">større betydning enn før, og at det i vår tid er et utbredt ønske om sterkere innsats i forebyggende</p><p align="left">helsearbeid. Det er påvist at i humusdekket i naturlig jordsmonn avtar innholdet av hovedbestandeler</p><p align="left">som natrium og magnesium stort sett med stigende avstand fra havet. Lignende lovmessigheter gjelder</p><p align="left">også for sporstoffer som jod, brom, klor og selen. I tillegg avtar disse også med nedbørsmengden. Dette</p><p align="left">tyder på at tilførsel av marine elementer til jordsmonn via nedbør er en meget viktig geokjemisk prosess,</p><p align="left">og de kan ha stor betydning for menneskers og dyrs helse. Endringer i nedbørens surhetsgrad og</p><p align="left">variasjoner i mengdeforholdet mellom de stoffer som tilføres jordsmonnet kan gi betydelige utslag i</p><p align="left">flora og fauna. Store befolkningsgrupper påvirkes til enhver tid av viktige kjemiske klimafaktorer, og</p><p align="left">det er sterkt ønskelig at forskning og veiledning innenfor dette fagfeltet intensiveres.</p><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><p align="left">Låg J.</p></span></span></span><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><p align="left"> </p></span></span><p align="left"><strong><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;"><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;">Chemical climate and health problems. </span></span></strong><em><span style="font-size: x-small; font-family: TimesNewRomanPS-ItalicMT;"><span style="font-size: x-small; font-family: TimesNewRomanPS-ItalicMT;">Nor J Epidemiol </span></span></em><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><span style="font-size: x-small; font-family: TimesNewRomanPSMT;">1998; </span></span><strong><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;"><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;">8 </span></span></strong><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><span style="font-size: x-small; font-family: TimesNewRomanPSMT;">(1): 19-20.</span></span></p><strong><span style="font-family: TimesNewRomanPS-BoldMT;"><span style="font-family: TimesNewRomanPS-BoldMT;"><p align="left"> </p></span></span><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;"><span style="font-size: x-small; font-family: TimesNewRomanPS-BoldMT;">ENGLISH SUMMARY</span></span></strong><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><span style="font-size: x-small; font-family: TimesNewRomanPSMT;"><p align="left">Physical factors of the climate have for a long time been considered to be of great interest. Variations in</p><p align="left">the chemical climate have received a growing attention only in the period after World War II, a trend</p><p align="left">which is due to an increasing interest in pollution and preventive health activities in our times. The</p><p align="left">contents of some of the major constituents in surface soil, such as sodium and magnesium, have been</p><p align="left">found to decrease with increasing distance from the sea. The contents of trace elements, such as iodine,</p><p align="left">bromine, chlorine, and selenium also show this type of distributional patterns, but in addition the</p><p align="left">contents in the soil of these elements increase with the amount of precipitation. Such data indicate that</p><p align="left">airborne transportation of elements from the sea to the continents is a geochemical process of great</p><p align="left">importance for most types of biological life. Great population groups are to a varying degree influenced</p><p>by factors of the chemical climate, and increased research activities in this field is desirable.</p></span></span>