Source regions of lower‐tropospheric airflow trajectories for the lower peninsula of Michigan: A 40‐year air mass climatology

Abstract

[1] Airflow trajectories were used to create a long-term (40-year) air mass climatology for the lower peninsula of Michigan. The climatology provides a necessary baseline for evaluating the impact of changes in airflow on historical and potential future variations in temperature and precipitation. Five-day back trajectories were calculated four times per day at the 925 hPa level using wind data from the NCEP/NCAR reanalysis fields. A Geographic Information System (GIS) was used to manage and display the large (58,440) volume of trajectories. The analysis revealed spatially coherent airflow pathways, and six resulting air mass source regions were defined. Also evident were large monthly variations in the frequency of trajectories from the major source regions. A residence time analysis performed within a GIS proved to be an efficient and effective means for summarizing the trajectories. Finally, a comparison of the results presented here to those of previous climatological analyses suggests that the choice of methodology has considerable influence on identification of the primary source regions for a location.

Anomalies of Central England Temperature Classified by Air Source

“…An alternative procedure could be to use ECMWF analyses and the Met Office's Numerical Atmospheric Dispersion Modeling Environment (NAME) model (Ryall and Maryon 1998), which is used operationally to track pollution episodes in three dimensions. Three-dimensional tracking is likely to be more accurate than single-level tracking in mountainous areas (Shadbolt et al 2006) and in regions of dynamically induced vertical motion (Stohl and Trickl 1999). NAME uses the 40-yr ECMWF Re-Analysis (ERA-40) and subsequent operational analyses, and this would allow optimized determination of sources of air daily from 1958 to the present, and residual anomalies of central England temperature could be estimated in near-real time.…”

Noble gas composition in rainwater and associated weather patterns

“…Although precipitation is reasonably well distributed throughout the year, peak precipitation occurs during summer months, mostly as thunderstorms under the influence of southerly air masses from the Gulf of Mexico. By contrast, cold air masses from the northwest Pacific and Canada are stronger from mid‐autumn to late spring [ Shadbolt et al ., ]. In addition, prevailing westerly winds bring some lake effect precipitation to the area during late fall and early winter.…”

“…By contrast, cold air masses from the northwest Pacific and Canada are stronger from mid-autumn to late spring [Shadbolt et al, 2006]. In addition, prevailing westerly winds bring some lake effect precipitation to the area during late fall and early winter.…”

A late Pleistocene–Mid‐Holocene noble gas and stable isotope climate and subglacial record in southern Michigan

“…Previous studies have hypothesized a change in air‐mass distribution over the Great Lakes region during the MH [ Krishnamurthy et al , 1995]. An increase in vapor transport from the Gulf of Mexico would lead to enriched δ 18 O values [see, e.g., Ma et al , 2004; Hall et al , 2012] as well as lower d‐excess values due to expected higher relative humidity at the Gulf of Mexico ocean source as compared to other moisture sources in the Midwest [ Shadbolt et al , 2006]. Our δ 18 O and d‐excess results from the late MH are consistent with this hypothesis.…”