Refine
Document Type
Language
- English (9)
Keywords
- Climate variability (1)
- Convective clouds (1)
- Data processing (1)
- Data quality control (1)
- Diurnal effects (1)
- ENSO (1)
- El Nino (1)
- Error analysis (1)
- Geographic location/entity (1)
- La Nina (1)
Institute
Europe and the Middle East
(2017)
In 2016, the dominant greenhouse gases released into Earth’s
atmosphere—carbon dioxide, methane, and nitrous oxide—
continued to increase and reach new record highs. The 3.5 ±
0.1 ppm rise in global annual mean carbon dioxide from 2015
to 2016 was the largest annual increase observed in the 58-
year measurement record. The annual global average carbon
dioxide concentration at Earth’s surface surpassed 400 ppm
(402.9 ± 0.1 ppm) for the first time in the modern atmospheric
measurement record and in ice core records dating back as
far as 800000 years.
One of the strongest El Niño events since at least 1950 dissipated in spring, and a weak La Niña evolved later in the year.
Owing at least in part to the combination of El Niño conditions
early in the year and a long-term upward trend, Earth’s surface
observed record warmth for a third consecutive year, albeit
by a much slimmer margin than by which that record was set
in 2015. Above Earth’s surface, the annual lower troposphere
temperature was record high according to all datasets analyzed,
while the lower stratospheric temperature was record low
according to most of the in situ and satellite datasets.
Several countries, including Mexico and India, reported
record high annual temperatures while many others observed
near-record highs. A week-long heat wave at the end of April
over the northern and eastern Indian peninsula, with temperatures surpassing 44°C, contributed to a water crisis for 330
million people and to 300 fatalities.
In the Arctic the 2016 land surface temperature was 2.0°C
above the 1981–2010 average, breaking the previous record of
2007, 2011, and 2015 by 0.8°C, representing a 3.5°C increase
since the record began in 1900. The increasing temperatures
have led to decreasing Arctic sea ice extent and thickness. On
24 March, the sea ice extent at the end of the growth season
saw its lowest maximum in the 37-year satellite record, tying
with 2015 at 7.2% below the 1981–2010 average. The September 2016 Arctic sea ice minimum extent tied with 2007 for the
second lowest value on record, 33% lower than the 1981–2010
average. Arctic sea ice cover remains relatively young and thin,
making it vulnerable to continued extensive melt. The mass of
the Greenland Ice Sheet, which has the capacity to contribute
~7 m to sea level rise, reached a record low value. The onset
of its surface melt was the second earliest, after 2012, in the
37-year satellite record.
Sea surface temperature was record high at the global scale,
surpassing the previous record of 2015 by about 0.01°C. The
global sea surface temperature trend for the 21st centuryto-date of +0.162°C decade−1 is much higher than the longer
term 1950–2016 trend of +0.100°C decade−1. Global annual
mean sea level also reached a new record high, marking the
sixth consecutive year of increase. Global annual ocean heat
content saw a slight drop compared to the record high in 2015.
Alpine glacier retreat continued around the globe, and
preliminary data indicate that 2016 is the 37th consecutive
year of negative annual mass balance. Across the Northern
Hemisphere, snow cover for each month from February to
June was among its four least extensive in the 47-year satellite
record. Continuing a pattern below the surface, record high
temperatures at 20-m depth were measured at all permafrost
observatories on the North Slope of Alaska and at the Canadian observatory on northernmost Ellesmere Island.
In the Antarctic, record low monthly surface pressures were
broken at many stations, with the southern annular mode setting record high index values in March and June. Monthly high
surface pressure records for August and November were set
at several stations. During this period, record low daily and
monthly sea ice extents were observed, with the November
mean sea ice extent more than 5 standard deviations below the
1981–2010 average. These record low sea ice values contrast
sharply with the record high values observed during 2012–14.
Over the region, springtime Antarctic stratospheric ozone
depletion was less severe relative to the 1991–2006 average,
but ozone levels were still low compared to pre-1990 levels.
Closer to the equator, 93 named tropical storms were observed during 2016, above the 1981–2010 average of 82, but
fewer than the 101 storms recorded in 2015. Three basins—the
North Atlantic, and eastern and western North Pacific—experienced above-normal activity in 2016. The Australian basin
recorded its least active season since the beginning of the
satellite era in 1970. Overall, four tropical cyclones reached
the Saffir–Simpson category 5 intensity level.
The strong El Niño at the beginning of the year that transitioned to a weak La Niña contributed to enhanced precipitation
variability around the world. Wet conditions were observed
throughout the year across southern South America, causing
repeated heavy flooding in Argentina, Paraguay, and Uruguay.
Wetter-than-usual conditions were also observed for eastern
Europe and central Asia, alleviating the drought conditions of
2014 and 2015 in southern Russia. In the United States, California had its first wetter-than-average year since 2012, after
being plagued by drought for several years. Even so, the area
covered by drought in 2016 at the global scale was among the
largest in the post-1950 record. For each month, at least 12% of
land surfaces experienced severe drought conditions or worse,
the longest such stretch in the record. In northeastern Brazil,
drought conditions were observed for the fifth consecutive
year, making this the longest drought on record in the region.
Dry conditions were also observed in western Bolivia and Peru;
it was Bolivia’s worst drought in the past 25 years. In May, with
abnormally warm and dry conditions already prevailing over
western Canada for about a year, the human-induced Fort
McMurray wildfire burned nearly 590000 hectares and became
the costliest disaster in Canadian history, with $3 billion (U.S.
dollars) in insured losses.
Sea salt (NaCl) has recently been proven to be of the utmost importance for ecosystem functioning in Amazon lowland forests because of its impact on herbivory, litter decomposition and, thus, carbon cycling. Sea salt deposition should generally decline as distance from its marine source increases. For the Amazon, a negative east–west gradient of sea salt availability is assumed as a consequence of the barrier effect of the Andes Mountains for Pacific air masses. However, this generalized pattern may not hold for the tropical mountain rainforest in the Andes of southern Ecuador. To analyse sea salt availability, we investigated the deposition of sodium (Na+) and chloride (Cl−), which are good proxies of sea spray aerosol. Because of the complexity of the terrain and related cloud and rain formation processes, sea salt deposition was analysed from both, rain and occult precipitation (OP) along an altitudinal gradient over a period between 2004 and 2009. To assess the influence of easterly and westerly air masses on the deposition of sodium and chloride over southern Ecuador, sea salt aerosol concentration data from the Monitoring Atmospheric Composition and Climate (MACC) reanalysis data set and back-trajectory statistical methods were combined. Our results, based on deposition time series, show a clear difference in the temporal variation of sodium and chloride concentration and Na+ ∕ Cl− ratio in relation to height and exposure to winds. At higher elevations, sodium and chloride present a higher seasonality and the Na+ ∕ Cl− ratio is closer to that of sea salt. Medium- to long-range sea salt transport exhibited a similar seasonality, which shows the link between our measurements at high elevations and the sea salt synoptic transport. Although the influence of the easterlies was predominant regarding the atmospheric circulation, the statistical analysis of trajectories and hybrid receptor models revealed a stronger impact of the north equatorial Atlantic, Caribbean, and Pacific sea salt sources on the atmospheric sea salt concentration in southern Ecuador. The highest concentration in rain and cloud water was found between September and February when air masses originated from the north equatorial Atlantic, the Caribbean Sea and the equatorial Pacific. Together, these sources accounted for around 82.4 % of the sea salt budget over southern Ecuador.
Atmospheric sulfur deposition above certain limits can represent a threat to tropical forests, causing nutrient imbalances and mobilizing toxic elements that impact biodiversity and forest productivity. Atmospheric sources of sulfur deposited by precipitation have been roughly identified in only a few lowland tropical forests. Even scarcer are studies of this type in tropical mountain forests, many of them megadiversity hotspots and especially vulnerable to acidic deposition. In these places, the topographic complexity and related streamflow conditions affect the origin, type, and intensity of deposition. Furthermore, in regions with a variety of natural and anthropogenic sulfur sources, like active volcanoes and biomass burning, no source emission data has been used for determining the contribution of each source to the deposition. The main goal of the current study is to evaluate sulfate (SO−4) deposition by rain and occult precipitation at two topographic locations in a tropical mountain forest of southern Ecuador, and to trace back the deposition to possible emission sources applying back-trajectory modeling. To link upwind natural (volcanic) and anthropogenic (urban/industrial and biomass-burning) sulfur emissions and observed sulfate deposition, we employed state-of-the-art inventory and satellite data, including volcanic passive degassing as well. We conclude that biomass-burning sources generally dominate sulfate deposition at the evaluated sites. Minor sulfate transport occurs during the shifting of the predominant winds to the north and west. Occult precipitation sulfate deposition and likely rain sulfate deposition are mainly linked to biomass-burning emissions from the Amazon lowlands. Volcanic and anthropogenic emissions from the north and west contribute to occult precipitation sulfate deposition at the mountain crest Cerro del Consuelo meteorological station and to rain-deposited sulfate at the upriver mountain pass El Tiro meteorological station.
The nitrogen cycle of tropical montane forest in Ecuador turns inorganic under environmental change
(2013)
[1] Water‐bound nitrogen (N) cycling in temperate terrestrial ecosystems of the Northern Hemisphere is today mainly inorganic because of anthropogenic release of reactive N to the environment. In little‐industrialized and remote areas, in contrast, a larger part of N cycling occurs as dissolved organic N (DON). In a north Andean tropical montane forest in Ecuador, the N cycle changed markedly during 1998–2010 along with increasing N deposition and reduced soil moisture. The DON concentrations and the fractional contribution of DON to total N significantly decreased in rainfall, throughfall, and soil solutions. This inorganic turn of the N cycle was most pronounced in rainfall and became weaker along the flow path of water through the system until it disappeared in stream water. Decreasing organic contributions to N cycling were caused not only by increasing inorganic N input but also by reduced DON production and/or enhanced DON decomposition. Accelerated DON decomposition might be attributable to less waterlogging and higher nutrient availability. Significantly increasing NO3‐N concentrations and NO3‐N/NH4‐N concentration ratios in throughfall and litter leachate below the thick organic layers indicated increasing nitrification. In mineral soil solutions, in contrast, NH4‐N concentrations increased and NO3‐N/NH4‐N concentration ratios decreased significantly, suggesting increasing net ammonification. Our results demonstrate that the remote tropical montane forests on the rim of the Amazon basin experienced a pronounced change of the N cycle in only one decade. This change likely parallels a similar change which followed industrialization in the temperate zone of the Northern Hemisphere more than a century ago.
[1] The formation of nocturnal convective clouds at the eastern Andes of south Ecuador and the adjacent Peruvian Amazon basin was investigated in a numerical model study. Their formation is expected to be an interactive procedure of nocturnal downslope flows in the Andean terrain, which forms a concave drainage system in the target area. Satellite imagery were used for both the identification of a sample case with a nocturnal cold cloud appearance and for the verification of the simulated results. The cloud patterns were distinguished on the basis of IR temperatures. A comparison of the data demonstrated the occurrence of a cold cloud shield in the target area, although the modeled cluster is significantly smaller. Further analysis of the development of the convective cells confirmed the assumed underlying processes. A strong current in the lower atmosphere, presumably a drainage flow, was recognizable in association with strong moisture convergence using a cross section through the cluster. Their presence was confirmed on the basis of their characteristic features and the surface energy fluxes as the driving force for thermally induced downslope flows.
Formation of Convective Clouds at the Foothills of the Tropical Eastern Andes (South Ecuador)
(2009)
This study examines the seasonal and diurnal dynamics of convective cloud entities—small cells and a mesoscale convective complex–like pattern—in the foothills of the tropical eastern Andes. The investigation is based on Geostationary Operational Environmental Satellite-East (GOES-E) satellite imagery (2005–07), images of a scanning X-band rain radar, and data from regular meteorological stations. The work was conducted in the framework of a major ecological research program, the Research Unit 816, in which meteorological instruments are installed in the Rio San Francisco valley, breaching the eastern Andes of south Ecuador. GOES image segmentation to discriminate convective cells and other clouds is performed for a 600 × 600 km2 target area, using the concept of connected component labeling by applying the 8-connectivity scheme as well as thresholds for minimum blackbody temperature, spatial extent, and eccentricity of the extracted components. The results show that the formation of convective clouds in the lowland part of the target area mainly occurs in austral summer during late afternoon. Nocturnal enhancement of cell formation could be observed from October to April (particularly February–April) between 0100 and 0400 LST (LST = UTC − 5 h) in the Andean foothill region of the target area, which is the relatively dry season of the adjacent eastern Andean slopes. Nocturnal cell formation is especially marked southeast of the Rio San Francisco valley in the southeast Andes of Ecuador, where a confluence area of major katabatic outflow systems coincide with a quasi-concave shape of the Andean terrain line. The confluent cold-air drainage flow leads to low-level instability and cellular convection in the warm, moist Amazon air mass. The novel result of the current study is to provide statistical evidence that, under these special topographic situations, katabatic outflow is strong enough to generate mainly mesoscale convective complexes (MCCs) with a great spatial extent. The MCC-like systems often increase in expanse during their mature phase and propagate toward the Andes because of the prevailing upper-air easterlies, causing early morning peaks of rainfall in the valley of the Rio San Francisco. It is striking that MCC formation in the foothill area is clearly reduced during the main rainy season [June–August (JJA)] of the higher eastern Andean slopes. At a first glance, this contradiction can be explained by rainfall persistence in the Rio San Francisco valley, which is clearly lower during the time of convective activity (December–April) in comparison with JJA, during which low-intensity rainfall is released by predominantly advective clouds with greater temporal endurance.
In this paper, the central Pacific cold event of 2008 and its exceptionally warm conditions in the eastern tropical Pacific are analyzed by using rainfall data of south Ecuadorian meteorological stations, sea surface temperatures in the El Niño3 and 1+2 regions, and simulations with the Weather Research and Forecasting (WRF) model. It can be shown that El Niño-like rainfall conditions with severe inundations occur particularly in the coastal plains of southern Ecuador while a central Pacific cold event prevails. In contrary to previous situations, positive rainfall anomalies as a result of El Niño-like conditions in the El Niño1+2 region during the 2008 La Niña event occurred in both regions, the coastal plains and the highlands, for the first time. A detailed analysis of the ocean-atmosphere system during episodes of heavy rainfall reveals typical El Niño circulation and rainfall patterns as observed during previous El Niño events for the coastal area and La Niña-like conditions for the highlands. The spreading of Pacific instability in the Niño1+2 region to the eastern escarpment of the Andes could be the result of a temporary eastward shift of the Walker circulation. The unusual combination of El Niño-like conditions in the eastern tropical Pacific during a La Niña state in the central Pacific is the newest indicator for an impact mode shift regarding severe rainfall anomalies during El Niño/La Niña events in the traditional El Niño area of southern Ecuador since the end of the last century. Since 2000, El Niño events unexpectedly provide below average rainfall while central Pacific La Niña conditions generate exceptional severe flooding in the normally drier coastal plains. The novel sea surface temperature (SST) anomaly dipole structure between the eastern and central/western tropical Pacific and the weakening of El Niño events since 2000 could be due to natural decadal oscillations in the El Niño background state, the Pacific Decadal Oscillation (PDO). However, the observed atmospheric patterns and the recent increase of the SST anomaly difference between the central and the eastern tropical Pacific resemble structures that also result from climate change simulations.
A New Class of Quality Controls for Micrometeorological Data in Complex Tropical Environments
(2015)
Quality control is a particularly demanding problem for micrometeorological studies in complex environments. With the transition to electronic sensing and storage of climate data in high temporal resolution, traditional approaches of homogenization are insufficient for addressing the small-scale variability and spatial heterogeneity of the data. This problem can be successfully addressed by introducing a new class of control procedures based on the physical and climatological relations between different climate variables. The new approach utilizes knowledge about the interdependency of air temperature, precipitation, radiation, relative air humidity, cloud cover, and visibility to develop empirical functions for determining the probability margins for the co-occurrence of specific conditions in tropical mountains and deserts. It can also be applied to other geographic settings by adjusting the parameters derived from the data itself. All procedures are integrated into a processing chain with feedback loops and combined with conventional logical and statistical checks, which enables it to detect small errors that normally pass unnoticed. The algorithms are also adapted to incorporate the short time steps of the original data to retain the potential for detailed process analyses.
Weather radar networks are indispensable tools for forecasting and disaster prevention in industrialized countries. However, they are far less common in the countries of South America, which frequently suffer from an underdeveloped network of meteorological stations. To address this problem in southern Ecuador, this article presents a novel radar network using cost-effective, single-polarization, X-band technology: the RadarNet-Sur. The RadarNet-Sur network is based on three scanning X-band weather radar units that cover approximately 87,000 km2 of southern Ecuador. Several instruments, including five optical disdrometers and two vertically aligned K-band Doppler radar profilers, are used to properly (inter) calibrate the radars. Radar signal processing is a major issue in the high mountains of Ecuador because cost-effective radar technologies typically lack Doppler capabilities. Thus, special procedures were developed for clutter detection and beam blockage correction by integrating ground-based and satelliteborne measurements. To demonstrate practical applications, a map of areas frequently affected by intense rainfall is presented, based on a time series of one radar that has been in operation since 2002. Such information is of vital importance to, for example, infrastructure management because rain-driven landslides are a major issue for road maintenance and safety throughout Ecuador. The presented case study of exceptionally strong rain events during the recent El Niño in March 2015 highlights the system’s practicality in weather forecasting related to disaster management. For the first time, RadarNet-Sur warrants a spatial-explicit observation of El Niño-related heavy precipitation in a transect from the coast to the highlands in a spatial resolution of 500 m.