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Fernando García-García

Bio: Fernando García-García is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Precipitation & Rain gauge. The author has an hindex of 6, co-authored 12 publications receiving 229 citations.

Papers
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TL;DR: In this article, the authors show that many intermediate sized raindrops fall up to an order of magnitude faster than expected and that these super-terminal drops are differently sized fragments of a recent break-up, moving with the speed of the parent drop and relaxing towards vt(D).
Abstract: [1] A unique relation between raindrop size and fall speed vt(D) is assumed throughout atmospheric science. Yet, our speed versus size measurements of millions of drops during natural rainfall events show that many intermediate sized raindrops fall up to an order of magnitude faster than expected. Furthermore, images of drop clusters reveal that these “super-terminal drops” are differently sized fragments of a recent break-up, moving with the speed of the parent drop and relaxing towards vt(D). Additional evidence of the break-up conjecture includes: (i) positive skewness in the distribution of fall speed deviations, (ii) strong size dependence of fall speed deviations and their maximum values and, (iii) preponderance of super-terminal drops in the presence of large raindrops (i.e., during periods of high rainfall rates).

102 citations

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TL;DR: In this paper, the influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and behaviour of clouds and their influence on climate, and a period of intensive measurements took place in December 2004 in Puerto Rico, using some of the latest developments in online instrumentation such as aerosol mass spectrometers, cloud condensation nuclei counters and a hygroscopicity tandem differential mobility analyser.
Abstract: The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and behaviour of clouds and their influence on climate. In an attempt to better understand warm cloud formation in a tropical marine environment, a period of intensive measurements took place in December 2004 in Puerto Rico, using some of the latest developments in online instrumentation such as aerosol mass spectrometers, cloud condensation nuclei counters and a hygroscopicity tandem differential mobility analyser. Simultaneous online measurements of aerosol size distributions, composition, hygroscopicity and optical properties were made near the lighthouse of Cape San Juan in the north-eastern corner of the island and at the top of East Peak mountain (1040 m a.s.l.), the two sites separated by 17 km. Additional measurements of the cloud droplet residual and interstitial aerosol properties were made at the mountain site, accompanied by measurements of cloud droplet size distributions, liquid water content and the chemical composition of cloud and rain water samples. Both aerosol composition and cloud properties were found to be sensitive to wind sector. Air from the east-northeast (ENE) was mostly free of anthropogenic influences, the submicron fraction being mainly composed of non-sea salt sulphate, while that from the east-southeast (ESE) was found to be moderately influenced by populated islands upwind, adding smaller ( −3 , median volume diameter decreased from 20 to 14 μm and the liquid water content increased from 0.24 to 0.31 g m −3 when the winds shifted from the ENE to ESE. Larger numbers of interstitial particles were recorded, most notably at sizes greater than 100 nm, which were absent during clean conditions. The average size of the residual particles and concentrations of cloudwater nitrate, sulphate and insoluble material increased during polluted conditions. Previous studies in Puerto Rico had reported the presence of a significant non-anthropogenic organic fraction in the aerosols measured and concluded that this was a factor controlling the in situ cloud properties. However, this was not observed in our case. In contrast to the 1.00±0.14 μg m −3 of organic carbon measured in 1992 and 1995, the organic matter measured in the current study of 0.17±0.35 μg m −3 is many times lower, most of which can be attributed to anthropogenic sources. During clean conditions, the submicron aerosol was observed to be almost entirely inorganic, an observation supported by the hygroscopicity measurements. This suggests that organic aerosols from marine sources may not be completely ubiquitous (either spatially or temporally) in this environment and requires further investigation to quantify their true extent and implications, with more extensive, longer-term sampling in conjunction with wind field analyses.

59 citations

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TL;DR: In this article, measurements of warm fog-droplet concentrations carried out in a site in Mexico were analyzed with the purpose of identifying inhomogeneous sections of clouds, and the results showed that a broadening of the droplet spectra towards larger sizes occurs in zones of decreased droplet concentration.

21 citations

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TL;DR: In this paper, an evaluation of precipitation estimations on the ground for individual rainfall events was carried out by comparing the 2B31 Tropical Rainfall Measuring Mission (TRMM) product versus a high-density, rain gauge network deployed at the ground over a small (about 1000 km2) study area in a continental region characterized by complex topography and high altitude.
Abstract: [1] An evaluation of precipitation estimations on the ground for individual rainfall events was carried out by comparing the 2B31 Tropical Rainfall Measuring Mission (TRMM) product versus a high-density, rain gauge network deployed at the ground over a small (about 1000 km2) study area in a continental region characterized by complex topography and high altitude. This comparison, using categorical analysis, showed a good agreement for several skill parameters most frequently used in works of this type. In this paper, it is concluded that Odds Ratio Skill Score (ORSS) is a more reliable measure of skill for categorical statistics than other scores because it better reflects the agreement between the two data sets. Furthermore, ORSS allows one to test the significance of the results so it is possible to discriminate whether the resulting skill is due to pure chance (ORSS was significant in 70% of the cases studied). Although variance and mean analyses generally showed differences between data sets for both the amount and the distribution of rainfall rate over the study area, least squares fits indicate a very high and quite linear correlation for both the mean rainfall rate (r2 = 0.90) and the maximum amount of precipitation at a given point (r2 = 0.74). It is concluded that 2B31 TRMM data can be used in weather applications for the area studied here and others with complex orographical characteristics and also as a tool in the diagnosis of individual rain events in other regions where there are no other data sources available.

13 citations


Cited by
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TL;DR: In this article, the authors discuss the role of chemical composition and particle size in cloud condensation nucleation processes, and the role that the chemical composition plays in the process of cloud droplet and ice nucleation.

1,347 citations

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TL;DR: In this article, the authors summarized past achievements related to the understanding of fog formation, development and decay, and in this respect, the analysis of observations and the development of forecasting models and remote sensing methods are discussed in detail.
Abstract: The scientific community that includes meteorologists, physical scientists, engineers, medical doctors, biologists, and environmentalists has shown interest in a better understanding of fog for years because of its effects on, directly or indirectly, the daily life of human beings. The total economic losses associated with the impact of the presence of fog on aviation, marine and land transportation can be comparable to those of tornadoes or, in some cases, winter storms and hurricanes. The number of articles including the word ``fog'' in Journals of American Meteorological Society alone was found to be about 4700, indicating that there is substantial interest in this subject. In spite of this extensive body of work, our ability to accurately forecast/nowcast fog remains limited due to our incomplete understanding of the fog processes over various time and space scales. Fog processes involve droplet microphysics, aerosol chemistry, radiation, turbulence, large/small-scale dynamics, and surface conditions (e.g., partaining to the presence of ice, snow, liquid, plants, and various types of soil). This review paper summarizes past achievements related to the understanding of fog formation, development and decay, and in this respect, the analysis of observations and the development of forecasting models and remote sensing methods are discussed in detail. Finally, future perspectives for fog-related research are highlighted.

544 citations

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TL;DR: In this article, a large number of published and unpublished measurements of cloud condensation nuclei (CCN) concentrations and aerosol optical thickness (AOT) measurements have been analyzed.
Abstract: . A large number of published and unpublished measurements of cloud condensation nuclei (CCN) concentrations and aerosol optical thickness (AOT) measurements have been analyzed. AOT measurements were obtained mostly from the AERONET network, and selected to be collocated as closely as possible to the CCN investigations. In remote marine regions, CCN0.4 (CCN at a supersaturation of 0.4%) are around 110 cm−3 and the mean AOT500 (AOT at 500 nm) is 0.057. Over remote continental areas, CCN are almost twice as abundant, while the mean AOT500 is ca. 0.075. (Sites dominated by desert dust plumes were excluded from this analysis.) Some, or maybe even most of this difference must be because even remote continental sites are in closer proximity to pollution sources than remote marine sites. This suggests that the difference between marine and continental levels must have been smaller before the advent of anthropogenic pollution. Over polluted marine and continental regions, the CCN concentrations are about one order of magnitude higher than over their remote counterparts, while AOT is about five times higher over polluted than over clean regions. The average CCN concentrations from all studies show a remarkable correlation to the corresponding AOT values, which can be expressed as a power law. This can be very useful for the parameterization of CCN concentrations in modeling studies, as it provides an easily measured proxy for this variable, which is difficult to measure directly. It also implies that, at least at large scales, the radiative and microphysical effects of aerosols on cloud physics are correlated and not free to vary fully independently. While the observed strong empirical correlation is remarkable, it must still be noted that there is about a factor-of-four range of CCN concentrations at a given AOT, and that there remains considerable room for improvement in remote sensing techniques for CCN abundance.

299 citations

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TL;DR: In this article, a new approach, TDMAinv, was proposed to represent the inverted GF-PDF as a piecewise linear function, where the convergence of the inversion is robust and independent of the initial guess.

266 citations

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TL;DR: Real-time mass spectrometry has been shown recently to provide the ability to probe the chemical composition of ambient individual particles <30 nm in diameter to further the understanding of how particles are formed through nucleation in the atmosphere.
Abstract: Many of the significant advances in our understanding of atmospheric particles can be attributed to the application of mass spectrometry. Mass spectrometry provides high sensitivity with fast response time to probe chemically complex particles. This review focuses on recent developments and applications in the field of mass spectrometry of atmospheric aerosols. In Part II of this two-part review, we concentrate on real-time mass spectrometry techniques, which provide high time resolution for insight into brief events and diurnal changes while eliminating the potential artifacts acquired during long-term filter sampling. In particular, real-time mass spectrometry has been shown recently to provide the ability to probe the chemical composition of ambient individual particles <30 nm in diameter to further our understanding of how particles are formed through nucleation in the atmosphere. Further, transportable real-time mass spectrometry techniques are now used frequently on ground-, ship-, and aircraft-based studies around the globe to further our understanding of the spatial distribution of atmospheric aerosols. In addition, coupling aerosol mass spectrometry techniques with other measurements in series has allowed the in situ determination of chemically resolved particle effective density, refractive index, volatility, and cloud activation properties.

235 citations