Μελέτη της πιθανής επίδρασης των δυναμικών θαλάσσσιων συνθηκών στους παράκτιους οικότοπους. Εφαρμογή στην Αφάντου Ρόδου

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Ναυτική και Θαλάσσια Τεχνολογία και Επιστήμη

The two types of El-Niño and their impacts on the length of day

International audienceAt the interannual to decadal timescale, the changes in the Earth rotation rate are linked with the El-Nin˜o Southern Oscillation phenomena through changes in the Atmospheric Angular Momentum. As climatic studies demonstrate that there were two types of El-Nin˜o events, namely Eastern Pacific (EP) and Central Pacific (CP) events, we investigate how each of them affect the Atmospheric Angular Momentum. We show in particular that EP events are associated with stronger variations of the Atmospheric Angular Momentum and length-of-day. We explain this difference by the stronger pressure gradient over the major mountain ranges, due to a stronger and more efficiently localized pressure dipole over the Pacific Ocean in the case of EP events

Extracting low frequency climate signal from GRACE data

International audienceFor more than four years, the GRACE pair of satellites have been orbiting the Earth, monitoring the time variable mass distribution for scales ranging from regional to global. The GRACE data have been released for a broad scientific community and sets of gravity fields are available. This paper shows that there are evidences at interrannual time scales for the presence of ENSO signal in the data, strongly correlated with the hydrological mass distribution, and also similar to the expected hydrological signature associated with the ENSO cycle. This signal dominates, at global scale, the one associated with geodynamic sources

ANALISA LAHAN KRITIS PADA SUB DAS AMBAWANG DENGAN SOFTWARE GEOGRAPHIC INFORMATION SYSTEM STUDI KASUS : TELUK BAKUNG, SUNGAI AMBAWANG, KUBU RAYA

Sub DAS Ambawang di Desa Teluk Bakung merupakan salah satu DAS Ambawang Kabupaten Kubu Raya Kalimantan Barat. Bencana banjir di beberapa tahun terakhir menunjukkan peningkatan, hal ini mengindikasikan telah terjadi gangguan siklus hidrologi di daerah aliran sungai. Oleh karena itu perlu dilakukan analisa penanganan yang serius untuk menentukan tingkat kekritisan lahan pada Sub DAS Ambawang yang nantinya dapat digunakan sebagai dasar perencanaan dalam upaya memulihkan dan meningkatkan fungsi Sub DAS sebagai ekosistem alam yang beperan dalam pengaturan siklus hidrologi. Penelitian ini bertujuan untuk menentukan tingkat kekritisan lahan pada Sub DAS Ambawang dan mengaplikasian GIS dalam menganalisa lahan kritis pada Sub DAS Ambawang. Parameter yang digunkan untuk menentukan lahan kritis antara lain penutupan lahan, kemiringan lereng, jenis tanah dan manajemen lahan. Metode yang digunakan adalah skoring, pembobotan dan overlay. Tingkat kekritisan lahan Sub DAS Ambawang terbagi menjadi 5 kelas, yaitu sangat kritis seluas 161,503 Ha, kritis seluas 3.080,109 Ha, agak kritis seluas 12.772,596 Ha, potensial kritis seluas 5.591,801 Ha, dan tidak kritis seluas 9.503,290 Ha. Pengaplikasian GIS dalam menganalisa lahan kritis pada Sub DAS Ambawang menghasilkan informasi yang dapat membantu dalam penanganan tata guna lahan untuk meningkatkan fungsi Sub DAS sebagai ekosistem alam yang beperan dalam pengaturan siklus hidrologi.Kata kunci: GIS, lahan kritis, overlay, Sub DAS Ambawan

Separating climate-induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements

We estimate the signature of the climate-induced mass transfers in repeated absolute gravity measurements based on satellite gravimetric measurements from the Gravity Recovery and Climate Experiment (GRACE) mission. We show results at the globe scale and compare them with repeated absolute gravity (AG) time behavior in three zones where AG surveys have been published: Northwestern Europe, Canada, and Tibet. For 10 yearly campaigns, the uncertainties affecting the determination of a linear gravity rate of change range 3–4 nm/s^2/a in most cases, in the absence of instrumental artifacts. The results are consistent with what is observed for long-term repeated campaigns. We also discuss the possible artifact that can result from using short AG survey to determine the tectonic effects in a zone of high hydrological variability. We call into question the tectonic interpretation of several gravity changes reported from stations in Tibet, in particular the variation observed prior to the 2015 Gorkha earthquake

Closure in the Earth's angular momentum budget observed from subseasonal periods down to four days: No core effects needed

International audienceShort period variations in the Earth's rotation rate, length‐of‐day (LOD), are driven mainly by the atmosphere with smaller contributions by the oceans. Previous studies have noted a lag of atmospheric angular momentum (AAM) with LOD that would imply another source. We examine AAM from the European Centre for Medium‐Range Weather Forecasts (ECMWF) and the National Centers for Environmental Prediction (NCEP) reanalysis series, along with oceanic angular momentum (OAM) from the ECCO consortium; land hydrological effects made no discernible impact. The NCEP reanalysis together with OAM produces a significant lag with LOD, while the ECMWF reanalysis AAM with OAM shows no phase lag. We find significant coherence with LOD variations down to periods of 4 days; coherence losses at shorter periods likely arise from the inverted barometer assumption and unmodeled dynamical processes. Thus the inclusion of core effects is not needed to balance the axial angular momentum budget on sub‐seasonal time scales