The thermal and chemical structure of the middle atmosphere is determined by molecules of air absorbing high-energy, solar, ultraviolet radiation. The dominant photochemical reaction for forming the stratosphere is dissociation of a molecule of oxygen into two atoms of oxygen. When a molecule is dissociated, the two pieces fly apart at high velocity. Temperature of air is directly proportional to the average velocity of all its molecules and atoms squared. Thus, photochemical dissociation converts bond energy efficiently and completely into air temperature. A molecule of oxygen is dissociated by absorbing ultraviolet-C radiation with frequencies around 1237 terahertz, energies around 5.1 electronvolts. Since oxygen makes up 20.95% of Earth’s atmosphere, there is ample oxygen to absorb all solar ultraviolet-C of appropriate frequencies that reaches the stratosphere, keeping the stratopause 30 to 40 oC warmer than the tropopause. Thus, the stratosphere forms an “electric” blanket warming Earth—electric in the sense that the thermal energy comes from a distant source, Sun, not from the body under the blanket, Earth. The second most important photochemical reaction in the stratosphere is dissociation of ozone by ultraviolet-B radiation with frequencies around 967 terahertz, energies around 4.0 electronvolts. While ozone concentrations, even in the ozone layer, are less than 10 parts per million, ozone is continually being formed and dissociated in the endless ozone-oxygen cycle, absorbing most solar ultraviolet-B radiation. When atoms of chlorine reach the lower stratosphere especially in winter, ozone concentrations that normally increase in winter can be depleted. One atom of chlorine, under the right conditions, can destroy 100,000 molecules of ozone. Depletion of the ozone layer allows more ultraviolet-B radiation than normal to reach Earth. Ultraviolet-B radiation is observed to cause sunburn, cataracts, skin cancer and mutations. It also dissociates ground-level ozone pollution, warming air in populated regions and penetrates oceans more than one hundred meters, very efficiently increasing ocean heat content as observed. Because of the ozone-oxygen cycle, where there are increased concentrations of ozone in the atmosphere, there is increased temperature. Sudden stratospheric warmings of 30-40 oC within days are typically associated with high concentrations of ozone and occur most frequently at altitudes of 30-50 km where dissociation of oxygen and ozone are most efficient. In 1798, Sir Benjamin Thompson proposed the mechanical theory of heat generated by friction when boring canon. This mechanical theory evolved into two fundamental assumptions: 1) heat is a flux of thermal energy measured in watts per square meter and 2) the greater the amount of flux absorbed, the hotter the body will become. Note that this approach never addresses the issue of what heat or thermal energy are, physically. (Complete abstract in poster file.)

Shortages of electricity in Colombia associated with droughts during El Niño-Southern Oscillation warm events lead government to seek diversification of the electricity matrix, which is mainly hydro (66%). Additionally, clean technologies like wind and solar power are alternatives to climate change. Potentially, solar radiation is high year-round in Colombia due to its low latitude, but clouds are the most critical limiting factor. In this paper, we measure and analyze the variations in efficiency resulting from different weather variables. Toward that end, we measure three photovoltaic systems located in three different zones of the valley. Simultaneously, we analyzed some of the limiting factors which influence solar radiation. For that, we consider radiation from 3 pyranometers, air temperature and relative humidity from meteorological sensors, water vapor density, liquid and solid water content from a microwave radiometer, reflectances as a proxy of clouds from GOES 16 satellite visible band 2. To identify clouds, we estimated radiance thresholds for the GOES information in the three locations of interest from changes in the surface radiation data. These thresholds provide identification of the most sensible hours for radiation based on the anomalies of the radiation under cloudiness conditions. Lastly, the efficiencies on each location were calculated considering the power data, as a proportion of the horizontal global radiation and the area of each solar panel.

The variabilities of the semidiurnal solar and lunar tide of the equatorial electrojet (EEJ) are investigated during the 2003, 2006, 2009 and 2013 major sudden stratospheric warming (SSW) events in this study. For this purpose, the ground-magnetometer recordings at the equatorial observatories in Huancayo and Fuquene are utilized. Results show a major enhancement in the amplitude of the EEJ semidiurnal lunar tide in each of the four warming events. The EEJ semidiurnal solar tidal amplitude shows an amplification prior to the onset of warmings, a reduction during the deceleration of the zonal mean zonal wind at 60°N and 10hPa and a second enhancement a few days after the peak reversal of the zonal mean zonal wind during all the four SSWs. Results also reveal that the amplitude of the EEJ semidiurnal lunar tide becomes comparable or even greater than the amplitude of the EEJ semidiurnal solar tide during all these warming events. The present study also compares the EEJ semidiurnal solar and lunar tidal changes with numerical simulations of the variability of the migrating semidiurnal solar (SW2) and lunar (M2) tide in neutral temperature at ~120km altitude. A better agreement between the enhancements of the EEJ semidiurnal lunar tide and the M2 tide in neutral temperature is observed in comparison with the enhancements of the EEJ semidiurnal solar tide and the SW2 tide in neutral temperature.

Numerical Weather Prediction models (NWP) have been used extensively since the ’40-’50s. Despite the advances in the field, the representation and forecast of the magnitude and variability of tropical processes in models is still a challenge. One of the steps to improve the precipitation forecasts using limited-area models is to evaluate which set of physical schemes and model domain configurations represent in a better way the actual behavior observed in the tropics. We implemented, as a part of a regional risk management strategy, two different operational weather forecast strategies for a complex terrain region in the Andes mountain range in northern South America. Both strategies, together, generate a total of eleven different forecasts every day, using the Weather Research and Forecasting model (WRF) with initial and boundary conditions from the Global Forecast System (GFS). The first configuration, implemented over five years ago and referred to as SYNAPSIS, includes three nested domains (18, 6 and 2 km) and is carried out every day using the 12 UTC GFS run and three different microphysics parametrizations: Eta Ferrier scheme, Purdue Lin Scheme and Thompson Scheme. The forecast lead-time of the latter strategy is 120 hours, and it does not use data assimilation. Since December of 2017, we implemented a second configuration termed RDFS, with two nested domains (12 and 2.4 Km), which carried out four times a day using the 00, 06, 12 and 18 UTC GFS runs. This configuration has a 30-hours lead time with the Thompson microphysics scheme. In RDFS, two WRF forecast runs are performed for each start hour, one assimilating weather radar reflectivity and the other without assimilation as control run, for a total of eight forecast runs daily. In this study, we assess the rainfall and temperature forecasts for all the different configurations using precipitation derived from reflectivity from weather radar, and air temperature at 2m from a network of automatic weather stations. We use 6 hourly and monthly skill scores (RMSE, BIAS, and Correlation coefficient) to quantify the precipitation differences between the SYNAPSIS and the RDFS configurations. To evaluate the impact of data assimilation in the precipitation forecast, we aggregate the results in a region within the inner domain, and then we calculate the average precipitation forecast between 0 and 36 predicted hours for RDFS with and without data assimilation. The results suggest a strong relationship between the forecast start time and the improve of precipitation forecast accuracy using data assimilation. The diurnal cycle of precipitation in the study region has a minimum in the morning (12 UTC) and a maximum in the afternoon (00 UTC) and during the night (09 UTC). The correspondence between the forecast improvement using data assimilation and the diurnal cycle of precipitation is likely due to the amount of assimilated data. In order to quantify the precipitation differences between the diffe

We present our first laboratory calibration and field results of a newly developed commercial ice nucleation chamber, the so-called PINE. The PINE instrument is developed based on the design of the AIDA cloud chamber (Möhler et al., 2003) to advance online atmospheric ice nucleation research. A unique aspect of the PINE chamber includes its plug-and-play feature (so it runs on a standard power outlet), autonomous cryo-cooler-based temperature-ramping operation, capability of quantifying INPs in different IN modes (e.g., immersion freezing and deposition mode at >-60 °C), small particle loss through the system (~5% for <5 m diameter particles), and sensitive optical particle detection of INP concentration (≤0.1 L-1 at T > -15 °C), promising stand-alone operation at remote locations. To date, the PINE chamber has been calibrated using test aerosol particles with known properties (e.g., illite NX). Briefly, test particles were exposed to ice supersaturation conditions, where a mixture of droplets and ice crystals were formed during the ‘expansion’ experiment. A comparison of our calibration test results to other techniques will be presented. Further, the PINE instrument has been tested in field campaigns in the Southern Great Plains. With a turnover time of ~6 minutes, PINE ran continuously and scanned at different temperature intervals to assess different INP episodes. We made sure to assess at least a few degrees of common temperature interval in a series of scan. Our first field results will be shown. Our results suggest that using this autonomous instrument may be critical to minimize error sources in high-temperature and supermicron INP research. Acknowledgement: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research (DE-SC0018979) – work packages 1-2 of Implications of Aerosol Physicochemical Properties Including Ice Nucleation at ARM Mega Sites for Improved Understanding of Microphysical Atmospheric Cloud Processes. References: • DeMott, P. J. et al. Resurgence in ice nuclei measurement research. Bull. Amer. Meteorol. Soc. 92, 1623, doi:10.1175/bams-d-10-3119.1 (2011). • Möhler, O. et al. Experimental investigation of homogeneous freezing of sulphuric acid particles in the aerosol chamber AIDA. Atmos. Chem. Phys. 3, 211-223 (2003).