Jorge F. Carrasco

Meteorological and Climatological Aspects of the Southern Patagonia Icefield

The Southern Patagonia Icefield (SPI) is located at mid-latitudes in southern South America, which is dominated by the westerly regime and frontal systems. This results in a high frequency of cloudy days (more than 70% of the time) and precipitation events. Analyses of air temperature and precipitation data from southern meteorological stations for the past century indicate an overall warming and decrease in precipitation until the mid-80’s, but no significant changes are observed afterwards. In fact, the coastal stations show an increase in precipitation after the 1980’s. The mid-term behavior of the atmospheric variables introduces uncertainties in predicting the consequences of future climate change in southern South America.

Secular trend of the equilibrium-line altitude on the western side of the southern Andes, derived from radiosonde and surface observations

The altitude of the 08C isotherm obtained from radiosonde data of the aerological Chilean stations Antofagasta, Quintero/Santo Domingo, Puerto Montt and Punta Arenas are analyzed, along with surface temperature and precipitation records from nearby stations. The strong effect of the 1976/ 77 climate shift due to a change in the Pacific Decadal Oscillation is evident in the temperature and precipitation data. The data are used as input for an empirical model which reconstructs annually the equilibrium-line altitude (ELA) for the last 49 years on the western side of the southern Andes. The model takes air temperature, precipitation and altitude as the main parameters, and was first developed by Fox (1993) and applied by Condom and others (2007). From the radiosonde data, a significant positive trend of the 08C isotherm has occurred in the northern, central and southern regions, indicating an ELA rise due to regional warming. General glacier retreat, ice thinning and negative mass balance observed during the past few decades in virtually all the Chilean Andes concur with the observed ELA reconstruction. In the Punta Arenas radiosonde record there is slight evidence for precipitation increase but no evidence for significant warming in the past few decades. This results in a slight lowering of the ELA according to the model reconstruction, which does not agree with the strong and increased glacier retreat observed in recent decades in Patagonia.

An analysis of ozone measurements at Cerro Tololo (30°S, 70°W, 2200 m.a.s.l.) in Chile

Increases in tropospheric ozone (O3) abundance are likely to take place in the near future in the populous and rapidly developing countries in the tropics and subtropics. An accurate evaluation of the future impact of increasing industrial activities in tropical and subtropical areas requires knowledge of the background levels of ozone. New ozone monitoring stations have been installed at several sites by the World Meteorological Organization (WMO) since the mid-90s. We analyze ozone data collected during two years since April 1996 at Cerro Tololo (30°S, 70°W, 2200 m.a.s.l.) some 50 km east from the city of La Serena. In this paper, we describe some of the atmospheric chemistry and meteorology that characterizes the Tololo site. The data show a seasonal variation with maximum mixing ratios in late winter and spring and minimum mixing ratios in late summer and early fall. These variations are most likely associated with the large-scale subsidence of the Hadley circulation and the location of the subtropical jet stream (STJ). Also, there is a diurnal variation that is probably partly associated with a mountain wind flow which is strongest in late spring and summer months. No significant mixing with marine boundary layer air perturbed by anthropogenic activities is apparent from the data. We find the Cerro Tololo site to be generally representative for background conditions of free-tropospheric air in the subtropics of the Southern Hemisphere. This work is done within the framework of a larger effort recently started by several Chilean institutions in cooperation with research centers abroad.

Spatio-temporal trends of precipitation, its aggressiveness and concentration, along the Pacific coast of South America (36–49°S)

ABSTRACT Precipitation is the most critical climatic element that directly affects the availability of water resources. The objective of this study was to describe and discuss spatio-temporal patterns of annual precipitation, its aggressiveness, and its concentration along the southwest coast of South America (36°–49°S) from 1930 to 2006. An annual and multi-decadal analysis was applied to 107 sampling stations distributed throughout this region, using the Mann-Kendall test (MK), and the Sampling Uncertainty Analysis (SUA) coupled with Gumbel probability density function (SUA-Gumbel). The analysis revealed positive but not significant trends in annual precipitation and aggressiveness for the region between 36° and 44°S, at least during the last 50 years of the analysed period. However, a significant decrease in annual precipitation and aggressiveness was observed between 44° and 49°S during the same period. The annual concentration of precipitation became slightly more seasonal in the last 50 years within the entire study area.

The first twenty years (1994–2014) of ozone soundings from Rapa Nui (27°S, 109°W, 51 m a.s.l.)

Ozone (O3) soundings have been performed on Easter Island or Rapa Nui (27 °S, 109 °W, 51 m a.s.l.) since 1994 as part of the Global Atmospheric Watch Programme of the World Meteorological Organization. In this work, we analyse 260 soundings compiled over the period 1994–2014, and make the data available for the international community. We characterise O3 profiles over this remote area of the Pacific by means of statistical analyses that consider, on the one hand, a traditional climatology that describes the data in terms of seasonal cycles based on monthly averages and, on the other hand, a process-oriented analysis based on self-organising maps. Our analyses show the influence of both tropical and subtropical/mid-latitude air masses at Rapa Nui. The former occurs in summer and fall when convective conditions prevail, and the latter in late winter and spring when subsiding conditions are recurrent. The occurrence of stratospheric intrusions in late winter and spring in connection with deep troughs and the presence of the subtropical jet stream is also apparent in the data set. The tropospheric ozone column is in good agreement with the corresponding data derived from satellites but with a systematic overestimate of summer and fall values. There is evidence of an upward trend in ozone near the surface, which suggests the impact of local pollution. We look forward to an enhancement of the Rapa Nui observing site, given its location that offers a privileged position to observe climate change over the sparsely sampled and vast South Pacific Ocean.

Red de estaciones de observación atmosférica en la Antártica, una colaboración internacional para la investigación del cambio climático

ABSTRACTThe Global Climate Observing System (GCOS) was established in 1992 by the World Meteorological Organization, the United Nation Environmental Program, the International Oceanography Commission and the International Council Scientific Union. This is as result of the Decision 11/CP.9 of the Fifth Con-ference of Parties of the Framework Convention for Climate Change of United Nation. GCOS is based on the compromise of the countries in maintaining the observing stations and providing the data. With this, GCOS accomplishes the goal of providing to the research community with a basic observing network for monitoring the climate system that will allow detecting the changes and responses of all components of the system. Antarctica is one of the regions for which GCOS has been essential for the observation and climate change research. Key words: GCOS, climate observation, climate system, climate change.RESUMENEl Sistema Mundial de Observacion del Clima fue establecido en 1992 por la Organizacion Me-teorologica Mundial, el Programa Medioambiental de Naciones Unidas, la Comision Oceanografica Intergubernamental y el Concejo Internacional para la Ciencia. Esto como respuesta a la

Snow Cover Change as a Climate Indicator in Brunswick Peninsula, Patagonia

Snow cover changes are assessed for the Brunswick Peninsula in southern Patagonia (52.9oS to 53.5oS), located on the transition between the wet Pacific Ocean area and the drier leeward side of the Andes. We use the Normalized Difference Snow Index (NDSI) and a new index which we call SnowPower, combining the NDSI and the Melt Area Detection Index (MADI), to reconstruct the snow cover extent and its temporal distribution for the period 2000-2016, based on Moderate Resolution Imaging Spectroradiometer Sensor (MODIS) MOD09GA products. Comparison of these satellite products with available snow duration and snow height data for 2010-2016 at the local Club Andino ski centre of Punta Arenas shows that the NDSI exhibits the best results. A reasonable and significant linear correlation is found between the MODIS NDSI snow cover extent and the mean monthly temperature at Punta Arenas Airport combined with the monthly snow accumulation at Jorge Schythe station at Punta Arenas city for the extended winter period (April to September) from 2000 to 2016. Snow cover changes within this time series are extended to 1972 and 1958 based on historical climate data of Jorge Schythe and Punta Arenas airport, repectively. The results show a significant decreasing trend of snow extent of 19% for Brunswick Peninsula for the 45-year period (1972-2016), which can be attributed to a statistically significant long-term warming of 0.71oC at Punta Arenas during the extended winter (April to September) in the same period. Multiple correlation with different climate variables indicates that solid precipitation has a relevant role on short-term snow cover variability, but is not related to the observed long-term snow cover decrease.

A low-cost UAS for monitoring vertical wind distribution

A low-cost Unmanned Aircraft System (UAS) has been developed based on commercial off-the-shelf components. The UAS includes a foam flying wing of expanded polypropylene with a 1.8 m wing-span and a total mass of 4 kg. It includes lithium polymer batteries which power a single propeller, resulting in a minimum airborne autonomy of 1 h. Experiments have been performed with a pitot tube to measure wind speed and wind direction on a vertical profile from 100 m a.s.l. to 3500 m a.s.l. A spiral pattern with a 100 m radius was followed on the ascent and descent. Results have been compared with radiosonde data obtained at Santo Domingo station located 80 km to the south. Wind data show a precision better than 1 m/s during the slower ascent stage and results are consistent with radiosonde data obtained 3 hours later at Santo Domingo station.

COMPORTAMIENTO DE LA TEMPERATURA DEL AIRE SUPERFICIAL EN EL GLACIAR FLEMING, PENÍNSULA ANTARTICA, DERIVADO DE UN SENSOR IN SITU

Un analisis sobre el comportamiento de la temperatura del aire al interior del Glaciar Fleming (GF),xa0ubicado en la Bahia Wordie en la parte central oeste de la Peninsula Antartica, es presentado en este estudio. Para tal efecto se utilizaron datos obtenidos in situ por una estacion meteorologica automatica (EMA), que registro los datos bajo condiciones de operacion continua (cada una hora), entre diciembre de 2007 y octubre de 2008. La EMA fue localiza a 50 km del frente del glaciar, aproximadamente 233 km al sur-suroeste de la estacion Rothera, y a una altitud de 1.057 m.s.n.m. Estos datos fueron complementados con observaciones meteorologicas registradas por EMAs circundantes que operan en la peninsula. Se encontraron significativas correlaciones estadisticas entre la EMA emplazada en el GF y lasxa0EMAs vecinas. La temperatura media mensual del aire registrada en la EMA al interior del GF vario entre -6,3 ± 0,1 y -22,3 ± 0,3 °C para el mes mas calido (enero) y frio (agosto), respectivamente. Mientras que el promedio anual, calculado con la media de verano e invierno de fue de -12.6 oC para el ano 2008. La altitud media de la isoterma Cero (ZIA, Zero Isotherm Altitud) para los dias con temperaturas sobre 0 °C, durante el verano (diciembre, enero y febrero) en la estacion Rothera, alcanzo los 390 m.s.n.m. La tendencia lineal para la ZIA revela un incremento en altura estadisticamente significativo de ~40 m para el periodo 1978-2010. La cota 390 m es alcanzada a alrededor de 15-17 km al interior del frente del glaciar, revelando que la mayor parte del GF y sus alrededores estan bajo las temperaturas decongelamiento durante todo el ano.