ABSTRACT:The Cordillera Vilcanota in the southern Peruvian Andes has been the site of significant research focused on paleoclimatic reconstructions from ice cores (Quelccaya), past glaciations, climate-glacier interactions, and ecological and human responses to climate change. In this article, we analyse precipitation patterns in the region from 2004 to 2010 using twice daily precipitation observations from six regional climate stations and hourly observations of precipitation intensity from nearby Cusco International Airport. We also analyse atmospheric fields of temperature, wind, and moisture at 700 and 200 hPa from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis dataset and create 72-h antecedent upstream air trajectories for the heaviest precipitation events using the National Oceanic and Atmospheric Administration (NOAA) Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Results indicate that the majority of annual precipitation across the cordilleras and inter-montane valleys alike occurs from nocturnal, regionally coherent rainfall events, inferred to be stratiform in structure, that occur in association with deep moist convection over adjacent Amazon lowlands. Low-level moisture (as inferred from the antecedent upstream air trajectories) for precipitation events can be supplied from a number of different regions, including from the northwest and west. The trajectory analysis reveals a strong dominance (83%) of precipitation events occur under weak flow regimes from nearby Amazon basin source regions, with 50% associated with trajectories from the northwest. In addition, the El Niño-Southern Oscillation (ENSO) signal reported in previous work in the central Andes is not necessarily representative of the Cordillera Vilcanota, where La Niña years (including 2007-2008) typically experience slightly below normal precipitation and El Niño years (including 2009-2010) are considerably wetter. These results are of particular value in understanding atmospheric signals registered in Andean low latitude ice cores, and point the way towards obtaining greater climatological inference from parameters preserved in annual snow and ice stratigraphy.

Precipitation processes and patterns in the southern Appalachian Mountains (SAM) are highly complex and varied due to the considerable diversity of synoptic-scale circulation patterns and associated orographic effects. Whereas frontal activity associated with extratropical cyclones is responsible for a large fraction of the annual precipitation in the region, 500 hPa cutoff lows, tropical cyclones, non-frontal air mass thunderstorms, and moist SE or NW low-level flow also produce considerable precipitation. This paper classifies the synoptic patterns associated with precipitation in the SAM over the course of a 16 mo period in 2009 and 2010. Precipitation events were identified using National Weather Service cooperative observer, Community Collaborative Rain, Hail, and Snow (CoCoRaHS), and other selected automated meteorological stations across the region. A combination of manual and automated approaches was used to create a synoptic classification of precipitation events in the SAM. Antecedent upstream air trajectories provided information on moisture source regions and low-level flow. Warm season precipitation events were influenced by air masses originating over the Gulf of Mexico and the Atlantic Ocean. These events were characterized by short periods of high-intensity precipitation that was primarily convective in nature. Cool season precipitation was associated with a variety of frontal types, as well as non-frontal mechanisms, characterized by longer, wetter, low-intensity events. These events were largely influenced by air masses originating over the Gulf of Mexico and to the northwest of the study area. In both seasons, precipitation events associated with frontal activity produced greater amounts of precipitation per event when compared with non-frontal activity.

Isotopic variation in northern and southern hard clam (quahog)shells is used in studies including paleoecology, paleoclimatology, and archaeology. It is unknown, however, whether species-specific isotopic differences exist. Three genotypes-Mercenaria mercenaria, M. campechiensis, and their natural hybrid form-are found in coastal Florida waters and differentiation of genotypes can be difficult to determine morphologically. This issue may be problematic when using archaeological shells as paleoclimate archives, because genetic analysis cannot be done on such specimens. Their co-occurrence in coastal Florida waters provides a unique opportunity to study whether all three genotypes of modern individuals record the same environmental information preserved as variation in oxygen and stable carbon isotope ratios. A random sample of 49 individuals collected alive at the same time and from the same locality in Pine Island Sound were classified to genotype using allozyme electrophoresis. Three juveniles from each genotype were selected for isotopic analysis to control for ontogenetic effects. Timing of growth increment formation inferred from oxygen isotope ratios reveals similar overall patterns wherein dark (slow growth) increments formed in mid-to late spring and light (fast growth) increments formed in late fall. Results of the mixed model ANOVA (analysis of variance) indicate that no significant species-related differences exist in the variation of oxygen and carbon isotope ratios, although the Kolmogorov-Smirnov goodness-of-fit test detected a systematic difference among ␦ 13 C values of M. mercenaria and M. campechiensis comparison and M. mercenaria and the hybrid shell comparison. Any genotype or combination thereof is, thus, suitable for environmental and climate reconstruction using oxygen isotope ratios. The utility of carbon isotope ratios as an environmental proxy, however, remains questionable.

There are many uncertainties associated with aerosol-precipitation interactions, particularly in mountain regions where a variety of processes at different spatial scales influence precipitation patterns. Statistical relationships between aerosols and precipitation were examined in the southern Appalachian Mountains to determine the seasonal and synoptic influences on these relationships, as well as the influence of air mass source region. Precipitation events were identified based on regional precipitation data and classified using a synoptic classification scheme developed for this study and published in a separate manuscript (Kelly et al. 2012). Hourly aerosol data were collected at the Appalachian Atmospheric Interdisciplinary Research (AppalAIR) facility at Appalachian State University in Boone, NC (1110 m asl, 36.215 • , -81.680 • ). Backward air trajectories provided information on upstream atmospheric characteristics and source regions. During the warm season (June-September), greater aerosol loading dominated by larger particles was observed, whereas cool season (November-April) precipitation events exhibited overall lower aerosol loading with an apparent influence from biomass burning particles. A significant relationship between aerosol optical properties and precipitation intensity was observed, which may be indicative of aerosol-induced precipitation enhancement in each season, particularly during warm season non-frontal precipitation.

There are many uncertainties associated with aerosol-precipitation interactions, particularly in mountain regions where a variety of processes at different spatial scales influence precipitation patterns. Aerosol-precipitation linkages were examined in the southern Appalachian Mountains, guided by the following research questions: (1) how do aerosol properties observed during precipitation events vary by season (e.g., summer vs. winter) and synoptic event type (e.g., frontal vs. non-frontal); and (2) what influence does air mass source region have on aerosol properties? Precipitation events were identified based on regional precipitation data and classified using a synoptic classification scheme developed for this study. Hourly aerosol data were collected at the Appalachian Atmospheric Interdisciplinary Research (AppalAIR) facility at Appalachian State University in Boone, NC (1110 m a.s.l., 36.215°, −81.680°). Backward air trajectories provided information on upstream atmospheric characteristics and source regions. During the warm season (June to September), greater aerosol loading dominated by larger particles was observed, while cool season (November to April) precipitation events exhibited overall lower aerosol loading with an apparent influence from biomass burning particles. Aerosol-induced precipitation enhancement may have been detected in each season, particularly during warm season non-frontal precipitation