Reconstructing northern Australian rainfall and the Central Indo-Pacific InterTropical Convergence Zone

The InterTropical Convergence Zone (ITCZ) delivers intense precipitation for the tropical regions of the globe. The Australian tropics receives ~80% of its annual mean rainfall in the wet season (November-April), influenced by the arrival of the Australian Summer Monsoon (ASM) as the ITCZ moves south of the equator. Northern Australian rainfall projections are uncertain due to a paucity in understanding the ITCZ dynamics, the ITCZ/ASM relationship, and the large internal variability of these climatic phenomena. This study explores Central-Indo-Pacific (CIP) ITCZ dynamics, using a new set of indices that better capture the ITCZ intensity, latitudinal width, centre and southern edge positions (S_edge); and by using the Sr/Ca record measured in a speleothem collected from Katherine, Northern Territory, Australia. Over the instrumental period, increases in ASM intensity and rainfall are correlated with southward latitudinal movements of the southern ITCZ edge (r = -0.71, -0.73 respectively, p \u3c 0.01). The southern edge is a function of ITCZ position and width, highlighting the problems with linking changes in paleo-ASM rainfall to latitudinal ITCZ movements alone. The southern ITCZ edge position is dominated by 3-year interannual variance, punctuated by shorter periods of ~7-year variance, over the instrumental period. The Sr/Ca records, covering ~1429-1478, ~1761-1777, ~1851-1870 and ~1885-1933, show robust seasonal signals modulated by hydrological change that also reflect S_edge and the dominance of 3- and 7-year periodicities. The 3-year cycling brings more intense rainfall totals and seasonality to the northern Australian region relative to the 7-year frequency, but longer Sr/Ca records are needed to assess their drivers

Canonical Correlation Analysis of Global Climate Elements and Rainfall in the West Java Regions

Indonesia has a diversity of climate influenced by several global phenomena such as El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and Asian-Australian Monsoon. Continuously climate changing indirectly causes a hydrometeorological disaster. The purpose of this study was to analyze the relationship between global climate elements (ENSO, IOD, Asian-Australian Monsoon) with rainfall in the West Java regions (Bogor Regency, Bandung Regency, Sukabumi Regency, Garut Regency, and Kuningan Regency) simultaneously. The selection of the five regions was based on the natural disaster reports of Badan Nasional Penanggulangan Bencana (BNPB). The research method used was a quantitative research method through one of multivariate analysis technique called canonical correlation analysis. The results of this study indicate that there was a simultaneous relationship between global climate elements, with rainfall in the West Java regions by 0.819. The global climate element and rainfall in the West Java regions that most influenced the relationship were Asian-Austalian Monsoon and Kuningan Regency rainfall

The Study of Wind Field ERA-20C in Monsoon Domains for Rainfall Predictor in Indonesia (Java, Sumatra, and Borneo)

In recent years, various research institutions have developed diverse global data reanalysis projects. This provides an opportunity to gain long-term of meteorological data for local scale. This study aims to select the potential predictor of wind fields u and v of the ERA-20C dataset, a reanalysis dataset, at 850 mb from seven domains or windows of Asian, Maritime Continent, Australian, and Western North Pacific monsoon related physically to rainfall anomaly patterns in Indonesia. The vector wind velocity scalar was obtained by using a Helmholtz decomposition to separate the total circulation v = (u,v) into the divergent component/velocity potential (χ) or Phi and rotational component/stream function (ψ) or Psi for obtaining the scalar variable of vector wind velocity. The method applied Singular value decomposition (SVD) to identify pairs of spatial patterns (expansion coefficients) between the predictors of Phi and Psi in seven domains, with rainfall data from 48 stations in Java, Sumatra, and Borneo Islands from 1981 to 2010. The results revealed that spatial patterns correlations of Java Islands were the highest in the Maritime Continent monsoon domain (80o−150o E and 15oS−15o N), while Sumatra and Borneo Island were in the Western North Pacific monsoon domain (100o–130o E and 5o–15o N) with predictor Psi. The lowest correlation for Java, Sumatra, and Borneo was the Australian monsoon domain (110o E–130o E and 5o S–15o S) with predictor Phi.  In general, spatial pattern correl-ations of Java Island were higher than others, agreeing with monsoonal rainfall type dominantly in the region

STATISTICAL ASSESSMENT OF SEDIMENT GRAIN SIZE AND ITS RELATION WITH SEASONAL AND ANNUAL CLIMATE VARIABILITY IN MUARA GEMBONG, JAKARTA BAY

Climate variability affects the properties of marine sediments. One of the sediment properties affected by climate is the grain size. This study is aimed to test the relation between sediment grain size and climate variability using sediment core GM01-2010-TJ22 that was acquired off Muara Gembong, which is part of Citarum river mouth. The samples were acquired in 2010 onboard RV. Geomarin I by Marine Geological Institute (MGI). Grain size analysis was conducted by Mastersizer 2000. The mean grain size is presented in time series for the 2001-2010 period. Then, the grain size sediment sample was correlated statistically with the seasonal (monsoon), annual, and interannual (El Niño/La Niña and Dipole Mode) phenomena. Data verification was conducted using secondary data of sea surface temperature from satellite images near the sediment sampling location and rainfall data in Bekasi. The verification result shows an increase in precipitation rate downriver of Citarum River followed by the decrease of sea surface temperature and larger grain size. The results using statistical test show that change of sediment sample`s grain size in Muara Gembong have significant correlation with Multivariate of ENSO (El Niño Southern Oscillation) Index (MEI), Ocean Niño Index (ONI), Dipole Mode Index (DMI) and Australian Monsoon Index (AUSMI). This result shows that sediment grain size can potentially be used to identify climate variability in Jakarta Bay.Variabilitas iklim dapat mempengaruhi sifat sedimen yang terendapkan di dasar laut. Salah satu sifat sedimen yang dipengaruhi oleh iklim adalah besar butir. Penelitian ini bertujuan untuk menguji hubungan antara besar butir dengan variabilitas iklim menggunakan sampel core GM01-2010-TJ22 dari Muara Gembong, Teluk Jakarta, muara sungai Citarum. Sampel core diambil pada tahun 2010 dengan menggunakan Kapal Riset Geomarin I oleh Pusat Penelitian dan Pengembangan Geologi Kelautan (P3GL). Pengukuran besar butir dilakukan dengan menggunakan Mastersizer 2000. Hasil pengukuran ditampilkan dalam seri waktu dari tahun 2001 sampai 2010. Hasil analisis besar butir sampel sedimen dikorelasikan secara statistik dengan fenomena musiman (monsun), tahunan dan antar tahun (El Niño/La Niña dan Dipole Mode). Verifikasi data dilakukan dengan menggunakan data sekunder temperatur permukaan laut dari citra satelit di sekitar lokasi sampel dan data curah hujan di Bekasi. Hasil verifikasi menunjukkan bahwa peningkatan curah hujan di sekitar daerah hilir Sungai Citarum diikuti dengan penurunan temperatur permukaan laut dan peningkatan ukuran rata-rata besar butir. Hasil yang didapat dalam uji statistika menunjukkan bahwa perubahan ukuran besar butir sampel sedimen di Muara Gembong memiliki korelasi signifikan dengan Multivariate ENSO (El Niño Southern Oscillation) Index (MEI), Ocean Niño Index (ONI), Dipole Mode Index (DMI) dan Australian Monsoon Index (AUSMI). Hasil tersebut menunjukkan bahwa besar butir sedimen dasar laut potensial digunakan untuk mengetahui variabilitas iklim di sekitar Teluk Jakarta

THE EFFECT OF THE ACTIVE USES OF SPREADSHEETS FOR MATHEMATICS INSTRUCTION WORKSHOP ON MATHEMATICS TEACHERS' SPREADSHEET ADOPTION

The pursuit of developing innovative learning environments in K-12 education has transformed many classrooms into technology-rich settings. I created a design-based professional development to support mathematics teachers’ adoption of spreadsheets as an instructional tool. The needs assessment study revealed that mathematics teachers’ perception and adoption of spreadsheets for mathematics instruction were low. This exploratory research study examined the effects of a design-based professional development on mathematics teachers’ spreadsheet knowledge, self-efficacy, usefulness and ease of use perceptions, and intentions to integrate spreadsheets into their instruction. A total of eight teachers engaged in approximately 20 hr of total workshop time, where some participants attended an online workshop and another group participated in an in-person offering. A comparison of preintervention and postintervention survey responses indicated that the Active Uses of Spreadsheets for Mathematics Instruction workshop effectively increased participants' scores on the Instructional Technology Adoption Survey. The response to interview questions suggests that the workshop was the catalyst for advanced participants’ understanding of how students can conceptually understand how to use spreadsheets to explore and analyze data. From a conventional perspective, they only viewed spreadsheets students use more procedural to complete mathematic calculations. Participants cited the demonstrations, the hands-on experience, and the collaboration as the reasons why the workshop successfully improved their knowledge and perceptions

Relationship of ENSO (El Niño – Southernoscillation ) and monsoon index on variability of rainfall and sea surface height in coastal City Semarang, Central Java

The city of Semarang is one of the coastal areas in Indonesia that is prone to flooding. Flood events that often occur in the Semarang City area can be triggered by high rainfall. Variations in rainfall and sea level are closely related to global atmospheric circulation such as ENSO and regional atmospheric circulation, Monsoon. This study aims to examine the relationship between ENSO and Monsoon with the distribution of rainfall and sea level in coastal city Semarang from 2012 to 2021. Correlation and composite analysis were used to analyze the relationship and impact of ENSO and Monsoon phenomena on rainfall and sea level. The results showed the strong correlation of the ENSO index (Southern Oscillation Index) to rainfall in the JJA and SON periods. Generally, El Niño (La Niña) has an impact on increasing (decreasing) rainfall. Meanwhile, Australian Summer Monsoon Index (AUSMI) only strongly correlates with rainfall in the SON period. The westerly (eastern) wind indicated by a positive (negative) monsoon index in the SON period has the effect of increasing (reducing) rainfall. The ENSO phenomenon with sea level during the JJA period has a strong relationship. In JJA, the highest sea level (maximum tide) rises by 12.6 cm during El Niño and decreases by 0.6 cm during La Niña. Meanwhile, the lowest sea level (minimum low tide) decreased by 16.6 cm during El Niño and increased by 0.7 cm during La Niña. These results can explain the influence of global and regional atmospheric circulation on a local scale on the coast of Semarang City. Keywords: Rainfall Sea level El Niño La Niña Monsoo

Analisis deret berkala multivariat dengan menggunakan model fungsi transfer : studi kasus curah hujan di Kabupaten Pati

Analisis data deret waktu pada dasarnya digunakan untuk melakukan analisis data yang mempertimbangkan pengaruh pengamatan periode sebelumnya. Analisis data deret waktu tidak hanya dapat dilakukan untuk satu variabel (univariat) tetapi juga dapat untuk banyak variabel (multivariat). Peranan peramalan banyak digunakan diberbagai bidang salah satunya adalah dalam bidang meteorologi yang peramalan cuaca dan curah hujan. Terdapat beberapa unsur cuaca yang mempengaruhi curah hujan, oleh menyangkut karena itu perlu dilakukan peramalan dengan menggunakan model multivariat. Pada model fungsi transfer terdapat deret output (yt) yang diperkirakan akan dipengaruhi deret input (xt) dan input-input lain yang digabungkan dalam satu kelompok yang disebut deret noise (nt). tujuan dari penelitian ini yaitu untuk meramalkan curah hujan bulanan di Kabupaten Pati dengan model fungsi transfer. Data yang digunakan dalam penelitian ini yaitu data curah hujan di Kabupaten Pati, Enso dan Ausmi dari tahun 2017 sampai tahun 2021. Hasil penelitian diperoleh model fungsi transfer sebagai berikut: yt=((1-0,95B)/(9,1-5,2B-7,7B^2))xt+(1/(1-0,91B))at Dengan menggunakan model tersebut diatas diperoleh hasil peramalan curah hujan di Kabupaten Pati tahun 2022 yaitu semakin mendekati akhir tahun curah hujan semakin berkurang. Puncak curah hujan terjadi dibulan Januari yaitu sebesar 113 mm dan curah hujan terendah di bulan Desember sebedar 62 mm