scholarly journals Assemblage structure and distribution of fish larvae on the North Kenya Banks during the Southeast Monsoon season

2021 ◽  
Vol 212 ◽  
pp. 105800
Author(s):  
James Mwaluma ◽  
Noah Ngisiang'e ◽  
Melckzedeck Osore ◽  
Joseph Kamau ◽  
Harrison Ong'anda ◽  
...  
Keyword(s):  
Fish Larvae ◽  
Monsoon Season ◽  
Assemblage Structure ◽  
The North ◽  
Distribution Of Fish

scholarly journals A snapshot on composition and distribution of fish larvae across the North Atlantic Ocean

2021 ◽  
Vol 22 (10) ◽  
Author(s):  
Mohd Nasarudin Harith ◽  
Cieran O'Donnell ◽  
GRAHAM JOHNSTON ◽  
Anne Marie Power
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Fish Assemblages ◽  
North Atlantic Ocean ◽  
Current Knowledge ◽  
Larval Fish ◽  
Fish Larvae ◽  
The North ◽  
The North Atlantic ◽  
Distribution Of Fish

Abstract. Harith MN, O’ Donnell C, Johnston G, Power AM. 2021. A snapshot on composition and distribution of fish larvae across the North Atlantic Ocean. Biodiversitas 22: 4496-4504. This study aims to describe the composition and distribution patterns of fish larvae communities across the North Atlantic Ocean. Several cruises were involved in the effort to collect the fish larvae samples. The sampling took place on the east side of the North Atlantic Ocean, towards the mid-Atlantic Ocean, and on the west side of the North Atlantic Ocean, near the eddies approaching Flemish Cap. A total of 9522 fish larvae were collected and identified from these surveys. These larvae came from 79 taxa and 29 families. Referring to the total abundance, considering all the sampled stations, Atlantic mackerel (Scomber scombrus) was the most abundant species (38.82% of the total fish larvae abundance), followed by blue whiting (Micromesistius poutassou) (15.9%). Referring to the Multi-dimensional scaling (MDS) ordination plots, two major stations clusters separate the on-shelf and off-shelf stations supported by SIMPER analysis. This study provides a snapshot of larval fish concentrations and assembly structure, but current knowledge suggests that the distribution of larval fish assemblages will be highly spatially variable, more research into plume front dynamics and their effects on the region's biota is needed to predict and understand changes.

scholarly journals CMIP5 Simulations of Low-Level Tropospheric Temperature and Moisture over the Tropical Americas

2013 ◽  
Vol 26 (17) ◽  
pp. 6257-6286 ◽  
Author(s):  
Leila M. V. Carvalho ◽  
Charles Jones
Keyword(s):  
Daily Precipitation ◽  
Monsoon Season ◽  
Coupled Model ◽  
Specific Humidity ◽  
Cmip5 Models ◽  
North American Monsoon ◽  
Tropospheric Temperature ◽  
The North ◽  
Decadal Variations ◽  
Monsoon System

Abstract Global warming has been linked to systematic changes in North and South America's climates and may severely impact the North American monsoon system (NAMS) and South American monsoon system (SAMS). This study examines interannual-to-decadal variations and changes in the low-troposphere (850 hPa) temperature (T850) and specific humidity (Q850) and relationships with daily precipitation over the tropical Americas using the NCEP–NCAR reanalysis, the Climate Forecast System Reanalysis (CFSR), and phase 5 of the Coupled Model Intercomparison Project (CMIP5) simulations for two scenarios: “historic” and high-emission representative concentration pathway 8.5 (RCP8.5). Trends in the magnitude and area of the 85th percentiles were distinctly examined over North America (NA) and South America (SA) during the peak of the respective monsoon season. The historic simulations (1951–2005) and the two reanalyses agree well and indicate that significant warming has occurred over tropical SA with a remarkable increase in the area and magnitude of the 85th percentile in the last decade (1996–2005). The RCP8.5 CMIP5 ensemble mean projects an increase in the T850 85th percentile of about 2.5°C (2.8°C) by 2050 and 4.8°C (5.5°C) over SA (NA) by 2095 relative to 1955. The area of SA (NA) with T850 ≥ the 85th percentile is projected to increase from ~10% (15%) in 1955 to ~58% (~33%) by 2050 and ~80% (~50%) by 2095. The respective increase in the 85th percentile of Q850 is about 3 g kg−1 over SAMS and NAMS by 2095. CMIP5 models project variable changes in daily precipitation over the tropical Americas. The most consistent is increased rainfall in the intertropical convergence zone in December–February (DJF) and June–August (JJA) and decreased precipitation over NAMS in JJA.

scholarly journals On the competition among aerosol number, size and composition in predicting CCN variability: a multi-annual field study in an urbanized desert

2015 ◽  
Vol 15 (12) ◽  
pp. 6943-6958 ◽  
Author(s):  
E. Crosbie ◽  
J.-S. Youn ◽  
B. Balch ◽  
A. Wonaschütz ◽  
T. Shingler ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Size Distribution ◽  
North American ◽  
Monsoon Season ◽  
Aerosol Size Distribution ◽  
North American Monsoon ◽  
Aerosol Composition ◽  
Data Set ◽  
The North ◽  
Concentration Changes

Abstract. A 2-year data set of measured CCN (cloud condensation nuclei) concentrations at 0.2 % supersaturation is combined with aerosol size distribution and aerosol composition data to probe the effects of aerosol number concentrations, size distribution and composition on CCN patterns. Data were collected over a period of 2 years (2012–2014) in central Tucson, Arizona: a significant urban area surrounded by a sparsely populated desert. Average CCN concentrations are typically lowest in spring (233 cm−3), highest in winter (430 cm−3) and have a secondary peak during the North American monsoon season (July to September; 372 cm−3). There is significant variability outside of seasonal patterns, with extreme concentrations (1 and 99 % levels) ranging from 56 to 1945 cm−3 as measured during the winter, the season with highest variability. Modeled CCN concentrations based on fixed chemical composition achieve better closure in winter, with size and number alone able to predict 82 % of the variance in CCN concentration. Changes in aerosol chemical composition are typically aligned with changes in size and aerosol number, such that hygroscopicity can be parameterized even though it is still variable. In summer, models based on fixed chemical composition explain at best only 41 % (pre-monsoon) and 36 % (monsoon) of the variance. This is attributed to the effects of secondary organic aerosol (SOA) production, the competition between new particle formation and condensational growth, the complex interaction of meteorology, regional and local emissions and multi-phase chemistry during the North American monsoon. Chemical composition is found to be an important factor for improving predictability in spring and on longer timescales in winter. Parameterized models typically exhibit improved predictive skill when there are strong relationships between CCN concentrations and the prevailing meteorology and dominant aerosol physicochemical processes, suggesting that similar findings could be possible in other locations with comparable climates and geography.

scholarly journals Seasonal Nature and Trends of Tropical Cyclone Frequency and Intensity over the North Indian Ocean

2020 ◽  
Vol 15 (3) ◽  
pp. 526-534
Author(s):  
Abhisek Pal ◽  
Soumendu Chatterjee
Keyword(s):  
Time Series ◽  
Tropical Cyclone ◽  
Indian Ocean ◽  
Monsoon Season ◽  
North Indian Ocean ◽  
Post Monsoon ◽  
The North ◽  
Increasing Trend ◽  
Post Monsoon Season ◽  
Cyclone Frequency

Tropical cyclone (TC) genesis over the North Indian Ocean (NIO) region showed significant amount of both spatial and temporal variability.It was observed that the TC genesis was significantly suppressed during the monsoon (June-September) compared to pre-monsoon (March-May) and post-monsoon (October-December) season specifically in terms of severe cyclonic storms (SCS) frequency. The Bay of Bengal (BoB) was characterized by higher TC frequency but lower intensity compared to the Arabian Sea (AS). It was also observed that the TC genesis locations were shifted significantly seasonally.The movement of the TCs also portrayed some significant seasonal differences. The pre-monsoon and post-monsoon season was responsible for generating TCs with higher values of accumulated cyclone energy (ACE) compared to the monsoon. The time series of TC frequency showed a statistically significant decreasing trend whereas the time series of ACE showed astatistically significant increasing trend over the NIO.

Frequency Modes of Monsoon Precipitation in Arizona and New Mexico

2006 ◽  
Vol 134 (12) ◽  
pp. 3774-3781 ◽  
Author(s):  
Anne W. Nolin ◽  
Eileen A. Hall-McKim
Keyword(s):  
New Mexico ◽  
Wavelet Analysis ◽  
Monsoon Season ◽  
Intraseasonal Variability ◽  
Low Frequency ◽  
North American Monsoon ◽  
Monsoon Precipitation ◽  
Monsoon Period ◽  
The North ◽  
Spectral Analysis Method

Abstract The interannual and intraseasonal variability of the North American monsoon is of great interest because a large proportion of the annual precipitation for Arizona and New Mexico arrives during the summer monsoon. Forty-one years of daily monsoon season precipitation data for Arizona and New Mexico were studied using wavelet analysis. This time-localized spectral analysis method reveals that periodicities of less than 8 days are positively correlated with mean daily precipitation during the 1 July–15 September monsoon period. Roughly 17% of the years indicate no significant periodicity during the monsoon period for either region and are associated with low monsoon precipitation. High- and low-frequency modes explain an equivalent percentage of the variance in monsoon precipitation in both Arizona and New Mexico, and in many years concurrent multiple periodicities occur. Wavelet analysis was effective in identifying the contribution of high-frequency modes that had not been discerned in previous studies. These results suggest that precipitation processes during the monsoon season are modulated by phenomena operating at synoptic (2–8 days) and longer (>8 days) time scales and point to the need for further studies to better understand the associated atmospheric processes.

scholarly journals Impact of the Desert dust on the summer monsoon system over Southwestern North America

2012 ◽  
Vol 12 (8) ◽  
pp. 3717-3731 ◽  
Author(s):  
C. Zhao ◽  
X. Liu ◽  
L. R. Leung
Keyword(s):  
North America ◽  
Radiative Forcing ◽  
Monsoon Season ◽  
Lower Atmosphere ◽  
Shortwave Radiation ◽  
Western Slope ◽  
Monsoon Circulation ◽  
The North ◽  
Moisture Fluxes ◽  
June July

Abstract. The radiative forcing of dust emitted from the Southwest United States (US) deserts and its impact on monsoon circulation and precipitation over the North America monsoon (NAM) region are simulated using a coupled meteorology and aerosol/chemistry model (WRF-Chem) for 15 years (1995–2009). During the monsoon season, dust has a cooling effect (−0.90 W m−2) at the surface, a warming effect (0.40 W m−2) in the atmosphere, and a negative top-of-the-atmosphere (TOA) forcing (−0.50 W m−2) over the deserts on 24-h average. Most of the dust emitted from the deserts concentrates below 800 hPa and accumulates over the western slope of the Rocky Mountains and Mexican Plateau. The absorption of shortwave radiation by dust heats the lower atmosphere by up to 0.5 K day−1 over the western slope of the Mountains. Model sensitivity simulations with and without dust for 15 summers (June-July-August) show that dust heating of the lower atmosphere over the deserts strengthens the low-level southerly moisture fluxes on both sides of the Sierra Madre Occidental. It also results in an eastward migration of NAM-driven moisture convergence over the western slope of the Mountains. These monsoonal circulation changes lead to a statistically significant increase of precipitation by up to ~40 % over the eastern slope of the Mountains (Arizona-New~Mexico-Texas regions). This study highlights the interaction between dust and the NAM system and motivates further investigation of possible dust feedback on monsoon precipitation under climate change and the mega-drought conditions projected for the future.

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