bluuebunny/crossref_metadata_2025 huggingface dataset:
الأداء الحركي المائي لشبكة الجر القاعى التقليدية في كوتا بارو من خلال تجربة خزان الممر المائي
Authors: أحمدي أحمدي
Published: January 2020

تم دراسة الأداء الحركي المائي لنموذج بمقياس 1: 8 من شبكة جر قاعي تقليدي في خزان ممر مائي. وهذا يمثل النموذج الأصلي لشبكة جر بقدرة موتور منخفضة تصل الى 33 حصان عند سرعة جر تصل الى 3 عقدة، والتي تعتبر شائعة الاستخدام في كوتابارو، إندونيسيا. فعند سرعة جر 3 عقدة (96 سم في الثانية للنموذج)، فان ارتفاعات الشبكة عند مسافات مختلفة بين أطراف الاجنحة تباينت بين 7 و9.2 سم، والمساحات البارزة لفتحة الشبكة من 6.35 × 210 الى 8.44 × 210 سم2، وحجم فلترة الماء من 32.04 × 310 الى 40.55 × 310 سم3، ومقاومة الشبكة الكلية من 11.07 × 210 الى 13.46 × 210 جم. وفي الدراسة الحالية، فان قيم النسبة H/a التي تم الحصول عليها كانت منخفضة (0.029 – 0.038) لأنه لم يكن هناك الجزء المربع في تركيب جسم الشبكة. وكان ارتفاع الشبكة 3.4% من محيط الشبكة وأصبحت اقل عند سرعات جر أعلى. ومن الممكن لسرعة مرور الماء وتوزيع الضغط حول الشبكة ان تغيير شكل عيون الشبكة من المعين الى متوازي الاضلاع. ومتوسط قيمة الأس 1.37 كانت أقل من القيمة المقترحة (2.0)، وعليه فإن شكل جسم الشبكة عند حالة الجر يجب أن يعاد تحديدها.
دراسة تجريبية على ستة أنواع من السرطانات المرتبطة بالشعاب المرجانية المحتملة الافتراس على كبسولات بيض بطنقدميات آكلة المرجان نوع: دروبيلا كورنس
Authors: جعفر بن عمر باعمر جعفر بن عمر باعمر
Published: January 2020

يتغذى الحلزون البطنقدمي دروبيلا كورنس (Drupella cornus)، والذي ينتمي لعائلة الميوريسيدي (Fmily : Muricidae) بشكل خاص على المستعمرات المرجانية، ويسبب تزايد أعدادها إلى وفيات أعداد كبيرة من المستعمرات المرجانية. حيث تضع إناث دروبيلا كورنس كبسولات بيضها على طبقات تحتية صلبة متاحة م على مدار العام؛ وتبلغ ذروة إطلاقها للكبسولات خلال الأشهر من مايو إلى يوليو ومن أكتوبر إلى يناير على ساحل جدة بالبحر الأحمر. و تهدف هذه الدراسة إلى التعرف على إمكانية افتراس كبسولات بيض دروبيلا كورنس من قبل ست سرطانات بحرية تعيش بداخل المستعمرات المرجانية تحت ظروف المختبر ولمدة 48 ساعة. وأظهرت النتائج تباين في معدلات افتراس السرطانات على كبسولات بيض دروبيلا كورنس؛ حيث سُجلت أعلى نسبة افتراس على كبسولات البيض 90% من إجمالي الكبسولات التي خضعت لاختبار السرطان سيكلوديو سنيتيدوس (Cyclodius nitidus)والذي تغذى بشراهة على كبسولات بيض دروبيلا كورنس، مقارنة بمعدل افتراس منخفضة جداً بنسبة 5% من اجمالي كبسولات البيض التي خضعت لاختبار السرطان ترابيزيا ديجيتاليس (Trapezia digitalis). كما أظهرت النتائج أن السرطان ترابيزيا بيدانتاتا(Trapezia bidentata) قد سبب إعطاب 30% من إجمالي كبسولات البيض دون فتحها والتغذية عليها. في حين لم يُلاحظ دلائل افتراس أو اثر هجوم على كبسولات بيض دروبيلا كورنس من قبل السرطانات الأخرى الثلاث ترابيزيا سيمودوس (Trapezia cymodoce) ، سيمو ميلانوداكتيلوس (Cymo melanodactylus) و سيدوليومير اسبيسيوسا(Pseudoliomera speciosa) . استخلصت النتائج أن السرطان سيكلوديوس نيتيدوس يعتبر مفترس مهم على كبسولات بيض دروبيلا كورنس؛ وهذا ما قد يجعله وسيلة مكافحة بيولوجية للحد من تزايد أعداد بطنقدميات آكلة المرجان دروبيلا كورنس.
تأثير المكملات الغذائية العشبية (® (MFAعلى التغذية، وترابط العليقة والوقاية من عدوى القناة الهضمية خلال فترة النمو في الاستزراع شبه المكثف لروبيان المحيط الهادئ أبيض الساق ليتوبينيس فانامي Litopenaeus vannamei (العائلة: Penaeidae)
Authors: ادوارد جورج ادوارد جورج
Published: January 2020

تمت دراسة تأثير المكملات الغذائية العشبية شبه اللزجة (نكهات غذائية متعددة)، التي أُعدت بالطبخ من خليط من النباتات (نبات الخولجان Alpinia glanga، نبات Trikatu ، ونبات الاملج الشائع Emblica officinalis، ونبات الشمرة الشائعة Foeniculum vulgare، ونبات باكوبا منيرة Bacopa monnieri، ونبات العبعب المنوم Withania somnifera) على التغذية، وملزمة العلف، والنمو، والعوامل المتغيرة للدم، والوقاية من الأمراض لروبيان المحيط الهادئ ذي الساق البيضاء نوع Litopenaeus vannamei. تم إجراء الفحوصات الفيزيائية للروبيان في منصة الفحص لمراقبة الحالة الصحية، وكفاءة تلقيم الأعلاف، ووقت التجفيف، وخصائص الأعلاف. كما تم تسجيل استهلاك العلف، ووقت التغذية، ومتوسط وزن الجسم (ABW). كما تم فحص العدد الكلي لخلايا الدم (THC)، ووقت التخثر. كما تمت مقارنة مدى فعالية المكملات الغذائية المتعددة ومكملات تجارية أخرى على تماسك العليقة. حيث وجد أن وقت جفاف عليقة المكملات الغذائية المتعددة كان أعلى (12 ±0.3 دقيقة) من العليقة المُعدة بنكهة تجارية (9 ±0.3 دقيقة) في حين كانت فترة التغذية على عليقة المكملات الغذائية المتعددة أعلى (169 ±8 دقيقة)، مقارنة بعليقة النكهة التجارية (73 ±6 دقيقة). وكان الحد الأقصى من العليقة المختبرة التي استهلكها الروبيان المختبر هي 8.1 ±0.3 كجم/100000 بذرة/ وجبة، في حين كانت 6.9 ±0.3 كجم/100000 بذرة/وجبة على روبيان مجموعة السيطرة، مع وجود اختلاف معنوي بين المجموعتين. تراوح الحد الأدنى لوقت التغذية ومتوسط وزن الجسم لروبيان المختبر ومجموعة السيطرة من 90 ±5 إلى120 ±5 دقيقة و 12.3 ±0.3 إلى 15.2 ±0.3 جرام على التوالي. وتراوح الحد الاقصى للعدد الكلي لخلايا الدم (THC) وفترة تخثر الخلايا اللمفية في عينات روبيان المختبر ومجموعة السيطرة التحكم من 59 ±2 (610 خلية/مل) إلى 67 ±2 ( 106خلية/مل) و 48 ±6 إلى 82 ±2 دقيقة على التوالي. تعد المكملات النباتية بمثابة مادة رابطة للعليقة، وتحسن أيضا النمو والمناعة للروبيان. وبالتالي، يمكن أن تكون هذه التركيبة مصدرًا طبيعيًا محتملاً للجزيئات النشطة بيولوجيًا للاستزراع المائي المستدام.
Экстремальные задачи в раскрасках гиперграфов
Authors: Raigorodskii Andrei Mikhailovich , Cherkashin Danila Dmitrievich
Published: January 2020

Экстремальные задачи в раскрасках гиперграфов неявно берут свое начало в теоремах Гильберта об одноцветных аффинных кубах (1892) и ван дер Вардена об одноцветных арифметических прогрессиях (1927). В дальнейшем, с появлением и развитием теории Рамсея, число задач о раскраске явно заданных гиперграфов росло. Однако систематическое изучение экстремальных задач о раскрасках гиперграфов началось с работ П. Эрдeша и А. Хайнала 60-х годов XX в. Данный обзор посвящен задачам о поиске гиперграфа с минимальным числом ребер, лежащего в некотором классе гиперграфов, их вариациям и приложениям. Центральной задачей такого типа является задача Эрдeша-Хайнала о нахождении минимального числа ребер в $n$-однородном гиперграфе с хроматическим числом не менее трех. Основная цель обзора - осветить обширные продвижения в этой области за последние несколько лет.
Библиография: 168 названий.
Этюды о резольвенте
Authors: Takhtadzhyan Leon Armenovich
Published: January 2020

Основываясь на понятии резольвенты и тождествах Гильберта, мы излагаем с единой точки зрения ряд классических результатов теории дифференциальных операторов и некоторые их приложения к теории автоморфных функций и теории чисел. Так, для оператора Штурма-Лиувилля приведен вывод формулы следов Гельфанда-Левитана, а для одномерного оператора Шрeдингера - вывод формулы Л. Д. Фаддеева для характеристического определителя и тождеств следов Захарова-Фаддеева. Далее излагаются недавно полученные результаты из спектральной теории одного функционально-разностного оператора, возникающего в конформной теории поля. Последний раздел обзора посвящен оператору Лапласа на фундаментальной области фуксовой группы первого рода на плоскости Лобачевского. Приводится алгебраическая схема доказательства аналитического продолжения ядра резольвенты оператора Лапласа и рядов Эйзенштейна-Мааса. В заключение обсуждается связь значений рядов Эйзенштейна-Мааса в точках Хегнера с дзета-функциями Дедекинда мнимых квадратичных полей и объясняется, почему использование псевдопараболических форм для случая модулярной группы не дает никакой информации о нулях дзета-функции Римана.
Библиография: 50 названий.
Интегрируемые биллиарды реализуют торические слоения на линзовых пространствах и 3-торе
Authors: Vedyushkina Viktoriya Viktorovna
Published: January 2020

В статье рассмотрен интегрируемый биллиард на книжке - комплексе, склеенном из нескольких биллиардов-листов вдоль общего корешка. Каждый лист - это плоская область, ограниченная дугами софокусных квадрик, биллиард в которой, как известно, интегрируем. Оказалось, что для ряда интересных случаев такого биллиарда инварианты Фоменко-Цишанга (меченые молекулы $W^*$) лиувиллевой эквивалентности описывают нетривиальные торические слоения на линзовых пространствах и 3-торе - изоэнергетических многообразиях таких биллиардов.
Библиография: 18 названий.
Спектральные представления топологических групп и почти открыто порожденные группы
Authors: Valov Vesko Marinov , Kozlov Konstantin Leonidovich
Published: January 2020

Вводится подкласс $\mathbb R$-факторизуемых групп - почти открыто порожденные группы. Он является топологическим и мультипликативным. Всюду плотная или открытая подгруппа, факторгруппа почти открыто порожденной группы и ее пополнение по Райкову - почти открыто порожденные группы. Почти связные про-лиевы группы, линделефовы почти метризуемые группы и пространства $C_p(X)$ непрерывных вещественнозначных функций на тихоновских пространствах в топологии поточечной сходимости - почти открыто порожденные группы. Приводятся характеризации почти открыто порожденных групп с использованием методов обратных спектров и теории топологических игр.
Библиография: 24 названия.
Существование и единственность слабого решения интегро-дифференциального уравнения агрегации на римановом многообразии
Authors: Vildanova Venera Fidarisovna
Published: January 2020

На компактном римановом многообразии $\mathscr{M}$ рассматривается класс интегро-дифференциальных уравнений агрегации с нелинейным параболическим членом $b(x,u)_t$. Дивергентный член в уравнениях может вырождаться с потерей коэрцитивности и содержит нелинейности с переменными показателями. Краевое условие "непротекания" на границе $\partial\mathscr{M}\times[0,T]$ цилиндра $Q^T=\mathscr{M}\times[0,T]$ обеспечивает при отсутствии внешних источников сохранение "массы" $\displaystyle\int_\mathscr{M}b(x,u(x,t)) d\nu=\mathrm{const}$. В цилиндре $Q^T$ с достаточно малым $T$ доказано существование ограниченного решения смешанной задачи для уравнения агрегации. При дополнительных условиях доказано существование ограниченного решения задачи в цилиндре $Q^{\infty}=\mathscr{M}\times[0,\infty)$. Для уравнений вида $b(x,u)_t=\Delta A(x,u)-\operatorname{div}(b(x,u)\mathscr{G}(u))+f(x,u)$ с оператором Лапласа-Бельтрами $\Delta$ и интегральным оператором $\mathscr{G}(u)$ доказана единственность ограниченного решения смешанной задачи.
Библиография: 26 названий.
Этальная монодромия и рациональная эквивалентность $1$-циклов на кубических гиперповерхностях в $\mathbb P^5$
Authors: Banerjee Kalyan , Guletskii Vladimir Igorevich
Published: January 2020

Пусть $k$ - несчетное алгебраически замкнутое поле характеристики $0$, и пусть $X$ - гладкое проективное связное многообразие размерности $2p$, вложенное в $\mathbb P^m$ над $k$. Пусть $Y$ - гиперплоское сечение $X$, и пусть $A^p(Y)$ и $A^{p+1}(X)$ - группы алгебраически тривиальных алгебраических циклов коразмерности $p$ и $p+1$ по модулю рациональной эквивалентности на $Y$ и $X$ соответственно. Предположим, что для гладкого $Y$ группа $A^p(Y)$ регулярно параметризована абелевым многообразием $A$ и совпадает с подгруппой классов степени $0$ в группе Чжоу $\operatorname{CH}^p(Y)$. Мы доказываем, что ядро гомоморфизма прямого образа из $A^p(Y)$ в $A^{p+1}(X)$ является объединением счетного числа сдвигов некоторого абелевого подмногообразия $A_0$ в $A$. Для очень общего гиперплоского сечения $Y$ или $A_0=0$, или $A_0$ совпадает с абелевым подмногообразием $A_1$ в $A$, касательное пространство к которому есть группа исчезающих циклов $H^{2p-1}(Y)_{\mathrm{van}}$. В конце статьи мы применяем эти общие результаты к сечениям гладкой четырехмерной кубики в $\mathbb P^5$.
Библиография: 33 названия.
Модель Изинга с немагнитным разбавлением на рекурсивных решетках
Authors: Semkin Sergei Viktorovich , Smagin Viktor Pavlovich , Gusev Evgeniy Georgievich
Published: January 2020

Методом составления самосогласованных уравнений построен класс приближенных решений задачи Изинга, являющихся обобщением приближения Бете. Показано, что некоторые из приближений этого класса можно интерпретировать как точные решения для модели Изинга на рекурсивных решетках. Для этих рекурсивных решеток найдены точные значения порогов протекания по узлам и связям и показано, что для модели Изинга разбавленного магнетика наш метод приводит к точным значениям для этих порогов.
Обобщенные операторы Пикара-Фукса, полученные из иерархии Уизема, в $\mathcal N$=2 суперсимметричной калибровочной теории с безмассовыми гипермультиплетами
Authors: Dai Jialiang
Published: January 2020

С помощью иерархии Уизема получены уравнения Пикара-Фукса в $\mathcal N$=2 суперсимметричной теории Янга-Миллса для классической калибровочной группы с $N_\mathrm{f}$ безмассовыми гипермультиплетами. В общем случае для $N_\mathrm{f}\ne 0$ существуют по крайней мере $r-2$ уравнения Пикара-Фукса, которые могут быть точно вычислены из коммутационных соотношений на мероморфные дифференциалы, определенные с точностью до линейной комбинации голоморфных дифференциалов на гиперэллиптической кривой Зайберга-Виттена. Изучаются уравнения Пикара-Фукса, включая инстантонные поправки, с применением техники оператора Эйлера. Кроме того, с помощью компьютерных символьных вычислений оказывается возможным получить полную совокупность уравнений Пикара-Фукса.
Дискретные теоремы Крама и решеточные уравнения типа КдФ
Authors: Zhang Cheng , Peng Linyu , Zhang Da-jun
Published: January 2020

Получены преобразования Дарбу и связанные с ними формулы Крама для двух разностных уравнений типа уравнения Шредингера, которые сами являются дискретными версиями спектральных задач для уравнений КдФ и модифицированных уравнений КдФ. Если рассматривать преобразования Дарбу как процесс дискретизации, то возникают классы полудискретных и полностью дискретных систем уравнений типа КдФ, включая решеточные версии потенцированного уравнения КдФ, потенцированного модифицированного уравнения КдФ и уравнения КдФ с шварцианом, как условия совместности дифференциальных/разностных спектральных задач и их преобразований Дарбу. Признаки интегрируемости фундаментальных решеточных моделей, такие как пара Лакса, многомерная совместность, $\tau$-функции и солитонные решения, можно легко получить в результате непосредственного применения дискретных формул Крама.
О динамике доменных стенок в цилиндрическом аморфном ферромагнитном микропроводе с магнитными неоднородностями
Authors: Leble Sergei Borisovich , Rodionova Valeriya Viktorovna
Published: January 2020

Исследована динамика доменной стенки в магнитном сердечнике тонких аморфных бистабильных микропроводов круглого сечения в стеклянной оболочке, содержащих
продольные неоднородности. Используется системный аналитический подход к задаче поиска частных решений непрерывной модели Гейзенберга, для чего используются уравнения Ландау-Лифшица-Гильберта. Установлена связь между структурой материала с дефектами и подвижностью доменной стенки, которая объясняет некоторые экспериментальные данные. Для заданного распределения дефектов в продольном направлении изучается влияние дефектов на распространение доменных стенок в бистабильных микропроводах в стеклянной оболочке. Получены новые ключевые формулы для скорости и ускорения доменной стенки на основе учета усредненного распределения дефектов.
Петли Вильсона в точных голографических ренормгрупповых потоках при нулевой и конечной температурах
Authors: Golubtsova Anastasiya Andreevna , Nguyen Vu Hoang
Published: January 2020

В контексте голографической дуальности изучаются прямоугольные времениподобные петли Вильсона для больших расстояний в точном ренормгрупповом потоке. Рассматривается пятимерная голографическая модель с экспоненциальным дилатонным потенциалом. Для исследования бэкграунда ренормгрупповых потоков при нулевой и конечной температурах вычисляются минимальные поверхности соответствующих струнных мировых листов. Показано, что голографический ренормгрупповой поток при $T=0$, который имитирует поведение бегущей константы связи квантовой хромодинамики, имеет фазу конфайнмента на больших расстояниях, в то время как ренормгрупповой поток с фиксированной точкой АдС в ультрафиолетовом пределе содержит только фазу деконфайнмента.
Квазиклассическая асимптотика нижних спектральных зон оператора Шредингера с тригонально-симметричным периодическим потенциалом
Authors: Anikin Anatolii Yur'evich , Vavilova Mariya Andreevna
Published: January 2020

Изучаются нижние спектральные зоны оператора Шредингера в квазиклассическом приближении с периодическим двумерным потенциалом, имеющим тригональную симметрию. Рассмотрены случаи, когда потенциал имеет одну или две ямы на элементарной ячейке. Получены экспоненциально малые асимптотики для ширины зоны, найдены дисперсионные соотношения. Исследован вид блоховских функций. Решение этой задачи представляет собой первый шаг в исследовании более сложной (и физически интересной) задачи о туннельных эффектах во вращающихся димерах.
Od prevoza do politike
Authors: Županek Bernarda , Miškec Alenka
Published: January 2020

Novembra 2015 so pri arheoloških raziskavah ob prenovi Slovenske ceste na prostoru emonske insule XIII med drugim odkrili železen prstan z vdelano gemo. Na njej je upodobljena bojna galeja. Razločno so vidna vesla, krma, kljun in oven (rostrum). Na ladji oziroma nad njo sta upodobljena signa militaria, vojaška znaka centurij. Prstan glede na obliko datiramo v 1. stoletje, gemo pa glede na stil izvedbe postavljamo v 1.–2. stoletje. Gema je bila izdelana v različici kalcedona, imenovanega nikolo. Prstani z gemami so služili za pečatenje različnih dokumentov, motivi na njih pa so odražali okus in identiteto lastnika. Geme z upodobitvami ladje so redke. Našli smo nekaj analogij, od katerih je naši po motivu najbližja ena od gem, ki jih hrani Britanski muzej v Londonu. Nadalje smo raziskovali vzor za motiv, in sicer na novcih, kjer so upodobitve ladje in/ali vojaških znakov v rimskem času pogoste. Zaradi zamejene datacije prstana smo iskanje vzora omejili na novce pozne republike in principata. Najbližje primerjave smo našli na seriji novcev Marka Antonija, ki so bili v velikih količinah kovani med 32–31 pr. n. š. pred pomorsko bitko pri Akciju. Na sprednji strani teh denarijev je podoba galeje z legendo, ki se nanaša na Antonijev položaj avgura in triumvira. Legende na zadnji strani omenjajo različne vojaške enote, upodobljeni pa so trije vojaški znaki: dva znaka centurij, kot na naši gemi, in orel (aquila), ki je bil znak legije. Domnevamo, da se je izdelovalec pri izdelavi motiva na naši gemi zgledoval po teh novcih ali kateri od podobnih serij.Upodobitev na naši gemi je vsekakor izstopajoča, saj so pomorski motivi v rimski gliptiki redki, sploh glede na pomen, ki ga je imela civilna in vojaška plovba za rimsko državo. Izbiro motiva lahko povezujemo z lastnikovo vojaško preteklostjo ali njegovim ponosom na pripadnost zmagoviti rimski državi.
The impact of biomass burning on upper tropospheric carbon monoxide: A study using MOCAGE global model and IAGOS airborne data
Authors: Cussac Martin , Marécal Virginie , Thouret Valérie , Josse Béatrice , Sauvage Bastien
Published: January 2020

Abstract. In this paper the fate of biomass burning emissions of carbon monoxide is studied with the global chemistry transport model MOCAGE and IAGOS airborne measurements for the year of 2013. The objectives are firstly to improve their representation within the model and secondly to analyse their contribution to carbon monoxide concentrations in the upper troposphere. At first, a new implementation of biomass burning injection is developed for MOCAGE, using the latest products available in GFAS biomass burning inventory on plume altitude and injection height. This method is validated against IAGOS observations of CO made in fire plumes, identified thanks to the SOFT-IO source attribution data. The use of these GFAS products lead to improved MOCAGE skill to simulate fire plumes originating from boreal forests wildfires. It was also shown that this new biomass burning injection method did not change upper tropospheric carbon monoxide concentrations elsewhere on the globe as the previous one was already satisfying. Then, MOCAGE performances were evaluated in general in the upper troposphere in comparison to the IAGOS database, and were shown to be very good, with very little bias and good correlations between the model and the observations. Finally, we analyse the contribution of biomass burning to upper tropospheric carbon monoxide concentrations. This was done by comparing simulations were biomass were toggled on and off in different source regions of the world to assess their individual influence. The two regions contributing the most to upper tropospheric CO were found to be the boreal forests and equatorial Africa, in accordance with the quantities of CO they emit each year and the fact that they undergo fast vertical transport: deep convection in the tropics and pyroconvection at high latitudes. It was found that biomass burning contributes for more than 11 % on average on the CO concentrations in the upper troposphere, and up to 50 % at high latitudes during the wildfire season.
Response of shortwave cloud radiative effect to greenhouse gases and aerosols and its impact on daily maximum temperature
Authors: Tang Tao , Shindell Drew , Zhang Yuqiang , Voulgarakis Apostolos , Lamarque Jean-Francois , Myhre Gunnar , Stjern Camilla W. , Faluvegi Gregory , Samset Bjørn H.
Published: January 2020

Abstract. Shortwave cloud radiative effects (SWCRE), defined as the difference of shortwave radiative flux between all-sky and clear-sky conditions, have been reported to play an important role in influencing the Earth’s energy budget and temperature extremes. In this study, we employed a set of global climate models to examine the SWCRE responses to CO2, black carbon (BC) aerosols and sulfate aerosols in boreal summer over the Northern Hemisphere. We found that CO2 causes positive SWCRE changes over most of the NH, and BC causes similar positive responses over North America, Europe and East China but negative SWCRE over India and tropical Africa. When normalized by effective radiative forcing, the SWCRE from BC is roughly 3–5 times larger than that from CO2. SWCRE change is mainly due to cloud cover changes resulting from the changes in relative humidity (RH) and, to a lesser extent, changes in circulation and stability. The SWCRE response to sulfate aerosols, however, is negligible compared to that for CO2 and BC. Using a multilinear regression model, it is found that mean daily maximum temperature (Tmax) increases by 0.15 K and 0.13 K per W m−2 increase in local SWCRE under the CO2 and BC experiment, respectively. When domain-averaged, the SWCRE change contribution to summer mean Tmax changes was 10–30 % under CO2 forcing and 30–50 % under BC forcing, varying by region, which can have important implications for extreme climatic events and socio-economic activities.
Inter-calibrating SMMR brightness temperatures over continental surfaces
Authors: Favrichon Samuel , Jimenez Carlos , Prigent Catherine
Published: January 2020

Abstract. Microwave remote sensing can be used to monitor the time evolution of some key parameters over land, such as land surface temperature or surface water extent. Observations are made with instrument such as the Scanning Microwave Multichannel Radiometer (SMMR) before 1987, the Special Sensor Microwave/Imager (SSM/I) and the following Special Sensor Microwave Imager/Sounder (SSMIS) from 1987 and still operating, to the more recent Global Precipitation Mission Microwave Imager (GMI). As these instruments differ on some of their characteristics and use different calibration schemes, they need to be inter-calibrated before long time series products can be derived from the observations. Here an inter-calibration method is designed to remove major inconsistencies between the SMMR and other microwave radiometers for the 18 GHz and 37 GHz channels over continental surfaces. Because of a small overlap in observations and a ~6 h difference in overpassing times between SMMR and SSM/I, GMI was chosen as a reference despite the lack of a common observing period. The diurnal cycles from three years of GMI brightness temperatures are first calculated, and then used to evaluate SMMR differences. Based on a statistical analysis of the differences, a simple linear correction is implemented to calibrate SMMR on GMI. This correction is shown to also reduce the biases between SMMR and SSM/I, and can then be applied to SMMR observations to make them more coherent with existing data record of microwave brightness temperatures over continental surfaces.
First Observations of the McMurdo-South Pole Ionospheric HF Channel
Authors: Chartier Alex Timothy , Vierinen Juha , Jee Geonhwa
Published: January 2020

Abstract. We present the first observations from a new low-cost oblique ionosonde located in Antarctica. The transmitter is located at McMurdo Station, Ross Island and the receiver at Amundsen-Scott Station, South Pole. The system was demonstrated successfully in March 2019, with the experiment yielding over 30 000 ionospheric echoes over a two-week period. These data indicate the presence of a stable E-layer and a sporadic and variable F-layer with dramatic spread-F of sometimes more than 500 km (in units of virtual height). The most important ionospheric parameter, NmF2, validates well against the Jang Bogo VIPIR ionosonde (observing more than 1000 km away). GPS-derived TEC data from the MIDAS algorithm can be considered necessary but insufficient to predict 7.2 MHz propagation between McMurdo and South Pole, yielding a true positive in 40 % of cases and a true negative in 73 % of cases. The success of this pilot experiment at a total grant cost of $116k and an equipment cost of ~$15k indicates that a large multi-static network could be built to provide unprecedented observational coverage of the Antarctic ionosphere.
Simultaneous measurement of the relative humidity dependent aerosol light extinction, scattering, absorption and single-scattering albedo with a humidified cavity-enhanced albedometer
Authors: Zhou Jiacheng , Xu Xuezhe , Zhao Weixiong , Fang Bo , Liu Qianqian , Cai Yuanqing , Zhang Weijun , Venables Dean S. , Chen Weidong
Published: January 2020

Abstract. Hygroscopic aerosols take up water and grow with increasing relative humidity (RH), giving rise to large changes in light extinction (bext), scattering (bscat), absorption (babs), and single scattering albedo (SSA, ω). The optical hygroscopic growth factors for each parameter (f(RH)ext,scat,abs,ω) are thus important for assessing aerosol effects on regional air quality, atmospheric visibility, and radiative forcing. The RH dependence of aerosol scattering and extinction has been studied in many laboratory and field studies. However, owing partly to the absence of suitable instrumentation, there are few reports of the RH dependence of aerosol absorption and ω. In this work, we report the development of a humidified cavity-enhanced albedometer (H-CEA) for simultaneous measurements of f(RH)ext,scat,abs,ω at λ = 532 nm from 10 % to 90 % RH. The instrument’s performance was evaluated with laboratory-generated ammonium sulphate, sodium chloride and nigrosin aerosols. Measured hygroscopic growth factors for different parameters were in good agreement with model calculations and literature reported values, demonstrating the accuracy of the H-CEA for measuring RH-dependent optical properties.
Lake mixing regime selects methane-oxidation kinetics of the methanotroph assemblage
Authors: Mayr Magdalena J. , Zimmermann Matthias , Dey Jason , Wehrli Bernhard , Bürgmann Helmut
Published: January 2020

Abstract. In freshwater lakes, large amounts of methane are produced in anoxic sediments. Methane-oxidizing bacteria effectively convert this potent greenhouse gas into biomass and carbon dioxide. These bacteria are present throughout the water column where methane concentrations can range from nanomolar to millimolar concentrations. In this study, we tested the hypothesis that methanotroph assemblages in seasonally stratified lakes are adapted to the contrasting methane concentrations in the epi- and hypolimnion. We further hypothesized that lake overturn would change the methane oxidation kinetics as more methane becomes available in the epilimnion. Together with the change of methane oxidation kinetics, we investigated changes in the transcription of genes encoding methane monooxygenase, the enzyme responsible for the first step of methane oxidation, with metatranscriptomics. We show that the half-saturation constant (Km) for methane, obtained from laboratory experiments with the natural microbial community, differed by two orders of magnitude between epi- and hypolimnion during stable stratification. During lake overturn, however, the kinetic constants in the epi- and hypolimnion converged along with a change of the transcriptionally active methanotroph assemblage. Conventional particulate methane monooxygenase appeared to be responsible for methane oxidation under different methane concentrations. Our results suggest that methane availability is important for creating niches for methanotroph assemblages with well-adapted methane-oxidation kinetics. This rapid selection and succession of adapted lacustrine methanotroph assemblages allows high methane removal efficiency of more than 90 % to be maintained even under rapidly changing conditions during lake overturn. Consequently, only a small fraction of methane stored in the anoxic hypolimnion is emitted to the atmosphere.
Twenty-first century ocean warming, acidification, deoxygenation, and upper ocean nutrient decline from CMIP6 model projections
Authors: Kwiatkowski Lester , Torres Olivier , Bopp Laurent , Aumont Olivier , Chamberlain Matthew , Christian James , Dunne John P. , Gehlen Marion , Ilyina Tatiana , John Jasmin G. , Lenton Andrew , Li Hongmei , Lovenduski Nicole S. , Orr James C. , Palmieri Julien , Schwinger Jörg , Séférian Roland , Stock Charles A. , Tagliabue Alessandro , Takano Yohei , Tjiputra Jerry , Toyama Katsuya , Tsujino Hiroyuki , Watanabe Michio , Yamamoto Akitomo , Yool Andrew , Ziehn Tilo
Published: January 2020

Abstract. Anthropogenic climate change leads to ocean warming, acidification, deoxygenation and reductions in near-surface nutrient concentrations, all of which are expected to affect marine ecosystems. Here we assess projections of these drivers of environmental change over the twenty-first century from Earth system models (ESMs) participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) that were forced under the CMIP6 Shared Socioeconomic Pathways (SSPs). Projections are compared to those from the previous generation (CMIP5) forced under the Representative Concentration Pathways (RCPs). 10 CMIP5 and 13 CMIP6 models are used in the two multi-model ensembles. Under the high-emission scenario SSP5–8.5, the model mean change (2080–2099 mean values relative to 1870–1899) in sea surface temperature, surface pH, subsurface (100–600 m) oxygen concentration and euphotic (0–100 m) nitrate concentration is +3.48 ± 0.78 °C, −0.44 ± 0.005, −13.27 ± 5.28 mmol m−3 and −1.07 ± 0.45 mmol m−3, respectively. Under the low-emission, high-mitigation scenario SSP1–2.6, the corresponding changes are +1.42 ± 0.32 °C, −0.16 ± 0.002, −6.36 ± 2.92 mmol m−3 and −0.53 ± 0.23 mmol m−3. Projected exposure of the marine ecosystem to these drivers of ocean change depends largely on the extent of future emissions, consistent with previous studies. The Earth system models in CMIP6 generally project greater surface warming, acidification, deoxygenation and euphotic nitrate reductions than those from CMIP5 under comparable radiative forcing, with no reduction in inter-model uncertainties. Under the high-emission CMIP5 scenario RCP8.5, the corresponding changes in sea surface temperature, surface pH, subsurface oxygen and euphotic nitrate concentration are +3.04 ± 0.62 °C, −0.38 ± 0.005, −9.51 ± 2.13 mmol m−3 and −0.66 ± 0.49 mmol m−3, respectively. The greater surface acidification in CMIP6 is primarily a consequence of the SSPs having higher associated atmospheric CO2 concentrations than their RCP analogues. The increased projected warming results from a general increase in the climate sensitivity of CMIP6 models relative to those of CMIP5. This enhanced warming results in greater increases in upper ocean stratification in CMIP6 projections, which contributes to greater reductions in euphotic nitrate and subsurface oxygen ventilation.
The phase space of last glacial inception for the Northern Hemisphere from coupled ice and climate modelling
Authors: Bahadory Taimaz , Tarasov Lev , Andres Heather
Published: January 2020

Abstract. We present an ensemble of Last Glacial Inception (LGI) simulations for the Northern Hemisphere that largely captures inferred ice volume changes within proxy uncertainties. This ensemble was performed with LCice 1.0, a coupled ice sheet and climate model, varying parameters of both climate and ice sheet components, as well as the coupling between them. Certain characteristics of the spatio-temporal pattern of ice growth and subsequent retreat in both North America (NA) and Eurasia (EA) are sensitive to parameter changes, especially with respect to regional rates of ice growth and retreat. We find that the initial inception of ice over NA and EA is best characterized by the nucleation of ice at high latitude and high elevation sites. Subsequent spreading and merger along with large-scale conversion of snow fields dominate in different sectors. The latter plays an important role in the merging of eastern and western ice regions in NA. The inception peak ice volume in the ensemble occurs approximately at 111 ka and therefore lags the summer 60° N insolation minimum by more than 3 kyr. Ice volumes consistently peak earlier over EA than NA. The inception peak in North America is characterized by a merged Laurentide and Cordilleran ice sheet, with Davis Strait covered in ice in 80 % of simulations. Ice also bridges Greenland and Iceland in all runs by 114 ka and therefore blocks Denmark Strait. This latter feature would thereby divert the East Greenland Current and Denmark Strait overflow and thereby potentially have a significant impact on ocean circulation. The Eurasian ice sheet at its inception peak varies across ensemble runs between a continuous ice sheet to multiple smaller ice caps. In both continents, the colder high latitudes (Ellsmere and Svalbard) tend to grow ice through the entire simulation (to 102 ka), while lower latitudes lose ice after 110 ka. We find temperature decreases over the initial phases of the inception lead to the expansion of NA ice sheet area, and that subsequent precipitation increases contribute to its thickening. EA ice sheet area also expands with decreasing temperatures, but sea ice limits any increases in precipitation, leading to an earlier retreat away from the EA maximum ice sheet volume. We also examine the extent to which the capture of both LGI ice growth and retreat constrains the coupled ice/climate model sensitivity to changing atmospheric pCO2. For a standard transient climate response experiment (1 % increase in pCO2 until doubled), warming ranges between 0.6–2.0 °C for our initial set of 500 simulations without LGI constraint. The warming is reduced to 0.7–1.4 °C for the 55 member ensemble that captures both LGI ice growth and retreat. This therefore underlines the potential value of fully coupled ice/climate modelling of last glacial inception to constrain future climate change.
Design methodology to determine the water quality monitoring strategy of a surface water treatment plant in the Netherlands
Authors: Ross Petra , van Schagen Kim , Rietveld Luuk
Published: January 2020

Abstract. The primary goal of a drinking water company is to produce safe drinking water
fulfilling the quality standards defined by national and international
guidelines. To ensure the produced drinking water meets the quality
standards, the sampling of the drinking water is carried out on a regular
(almost daily) basis. It is a dilemma that the operator wishes to have a
high probability of detecting a bias while minimizing their measuring effort.
In this paper a seven-step design methodology is described which helps to
determine a water quality (WQ) monitoring scheme. Besides using soft sensors as
surrogate sensors for parameters currently not available online, they can
possibly provide a cost-effective alternative when used to determine
multiple parameters required through one single instrument.
A17-year dataset of surface water fugacity of CO2, along with calculated pH, Aragonite saturation state, and air-sea CO2 fluxes in the Northern Caribbean Sea
Authors: Wanninkhof Rik , Pierrot Denis , Sullivan Kevin , Barbero Leticia , Trinanes joaquin
Published: January 2020

Abstract. A high-quality dataset of surface water partial pressure/fugacity of CO2 (pCO2w/fCO2w), comprised of over a million observations, and derived products are presented for the Caribbean Sea covering the timespan from 2002 through 2018. Prior to installation of automated pCO2 systems on cruise ships of the Royal Caribbean Cruise Lines and subsidiaries, very limited surface water carbon data were available in this region. With this observational program, the Northern Caribbean Sea has now become one of the best sampled regions for pCO2 of the world's ocean. The dataset, and derived quantities are provided on a 1-degree monthly grid at http://accession.nodc.noaa.gov/0207749, DOI: https://doi.org/10.25921/2swk-9w56 (Wanninkhof et al., 2019a). The derived quantities include total alkalinity (TA), acidity (pH), Aragonite saturation state (ΩAr) and air-sea CO2 flux, and cover the region from 15° N to 28° N and 88° W to 62° W. The data and products are used for determination of status and trends of ocean acidification, for quantifying air-sea CO2 fluxes, and for ground truthing models. Methodologies to derive the inorganic carbon system parameters and to calculate the fluxes from fCO2w are described.
New analytical and data evaluation protocols to improve the
reliability of U-Pb LA-ICP-MS carbonate dating
Authors: Guillong Marcel , Wotzlaw Jören-Frederik , Looser Nathan , Laurent Oscar
Published: January 2020

Abstract. We document that the reliability of carbonate U-Pb dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is improved by matching the aspect ratio of the LA single hole drilling craters and propagating of long-term excess uncertainty and systematic uncertainties. We investigated the impact of different matrices and ablation crater geometries using U-Pb isotope analyses of one primary (WC-1) and two secondary reference materials (RMs). Validation RMs (VRM) include a previously characterized (ASH-15D) and a new candidate (JT), characterized by ID-TIMS (intercept age: 13.797 ± 0.031 Ma) with excellent agreement to pooled LA-ICP-MS measurements (13.81 ± 0.11 ¦ 0.30 Ma), U concentration of approx. 1 μg/g and 238U/206Pb ratios from 5 to 460, well defining the isochron. Differences in ablation crater depth to diameter ratios (aspect ratio) introduce an offset due to downhole fractionation and/or matrix effects. This effect can be observed either when the crater size between U-Pb RM and sample changes or when the ablation rate for the sample is different than for the RM. Observed deviations are up to 20 % of the final intercept age depending on the degree of crater geometry mismatch. The long-term excess uncertainty was calculated to be in the range of 2 % (ASH-15D) to 2.5 % (JT), and we recommend propagating this uncertainty into the uncertainty of the final results. Additionally, a systematic offset to the ID-TIMS age of 2–3 % was observed for ASH-15D but not for JT. This offset might be due to different ablation rates of ASH-15D compared to the primary RM or remaining matrix effects, even when chosen aspect ratios are similar.
SEAMUS (v1.20): a Δ14C-enabled, single-specimen sediment accumulation simulator
Authors: Lougheed Bryan C.
Published: January 2020

Abstract. The systematic bioturbation of single particles (such as foraminifera)
within deep-sea sediment archives leads to the apparent smoothing of any
temporal signal as recorded by the downcore, discrete-depth mean signal. This
smoothing is the result of the systematic mixing of particles from a wide
range of depositional ages into the same discrete-depth interval. Previous
sediment models that simulate bioturbation have specifically produced an
output in the form of a downcore, discrete-depth mean signal. However,
palaeoceanographers analysing the distribution of single foraminifera
specimens from sediment core intervals would be assisted by a model that
specifically evaluates the effect of bioturbation upon single specimens.
Taking advantage of advances in computer memory, the single-specimen
SEdiment AccuMUlation Simulator (SEAMUS) was created for MATLAB and Octave,
allowing for the simulation of large arrays of single specimens. This model
allows researchers to analyse the post-bioturbation age heterogeneity of
single specimens contained within discrete-depth sediment core intervals
and how this heterogeneity is influenced by changes in sediment accumulation
rate (SAR), bioturbation depth (BD) and species abundance. The simulation
also assigns a realistic 14C activity to each specimen, by considering
the dynamic Δ14C history of the Earth and temporal changes in
reservoir age. This approach allows for the quantification of possible
significant artefacts arising when 14C-dating multi-specimen samples
with heterogeneous 14C activity. Users may also assign additional
desired carrier signals to single specimens (stable isotopes, trace
elements, temperature, etc.) and consider a second species with an
independent abundance. Finally, the model can simulate a virtual
palaeoceanographer by randomly picking whole specimens (whereby the user can
set the percentage of older, “broken” specimens) of a prescribed sample size
from discrete depths, after which virtual laboratory 14C dating and
14C calibration is carried out within the model. The SEAMUS
bioturbation model can ultimately be combined with other models (proxy and
ecological models) to produce a full climate-to-sediment model workflow,
thus shedding light on the total uncertainty involved in palaeoclimate
reconstructions based on sediment archives.
AtChem (version 1), an open-source box model for the Master Chemical Mechanism
Authors: Sommariva Roberto , Cox Sam , Martin Chris , Borońska Kasia , Young Jenny , Jimack Peter K. , Pilling Michael J. , Matthaios Vasileios N. , Nelson Beth S. , Newland Mike J. , Panagi Marios , Bloss William J. , Monks Paul S. , Rickard Andrew R.
Published: January 2020

Abstract. AtChem is an open-source zero-dimensional box model for atmospheric
chemistry. Any general set of chemical reactions can be used with
AtChem, but the model was designed specifically for use with the
Master Chemical Mechanism (MCM, http://mcm.york.ac.uk/, last access: 16 January 2020).
AtChem was initially developed within the EUROCHAMP project as a web
application (AtChem-online, https://atchem.leeds.ac.uk/webapp/, last access: 16 January 2020)
for modelling environmental chamber experiments; it was recently
upgraded and further developed into a stand-alone offline version
(AtChem2), which allows the user to run complex and long
simulations, such as those needed for modelling of intensive field
campaigns, as well as to perform batch model runs for sensitivity
studies. AtChem is installed, set up and configured using
semi-automated scripts and simple text configuration files, making
it easy to use even for inexperienced users. A key feature of
AtChem is that it can easily be constrained to observational data
which may have different timescales, thus retaining all the
information contained in the observations. Implementation of a
continuous integration workflow, coupled with a comprehensive suite
of tests and version control software, makes the AtChem code base
robust, reliable and traceable. The AtChem2 code and documentation
are available at https://github.com/AtChem/ (last access: 16 January 2020) under the open-source MIT License.
65-year changes of annual streamflow volumes across Europe with a focus on the Mediterranean basin
Authors: Masseroni Daniele , Camici Stefania , Cislaghi Alessio , Vacchiano Giorgio , Massari Christian , Brocca Luca
Published: January 2020

Abstract. Determining the spatio-temporal variability of annual streamflow volume plays a relevant role in hydrology for improving and implementing sustainable and resilient policies and practices of water resource management. This study investigates annual streamflow volume trends in a newly-assembled, consolidated and validated dataset of daily mean river flow records from more than 3,000 stations, which cover near-natural basins in more than 40 countries across Europe. Although the dataset contains streamflow time-series from 1850 to 2015 in some stations, the statistical analyses were carried out by including observations from 1950 to 2015 in order to have a consistent and reliable dataset over the continent. Trends were detected calculating the slope of Theil-Sen's line over the annual anomalies of streamflow volume. The results show annual streamflow volume trends emerged at European scale, with a marked negative tendency in Mediterranean regions (about −1 × 103 m3/(km2 year)) and a generally positive trend in northern ones (about 0.5 × 103 m3/(km2 year)). The annual streamflow volume trend patterns appear in agreement with the continental-scale climate change observations in response to climate change drivers. In the Mediterranean area, the declining of annual streamflow volumes started in 1965 and since early 80' volumes are consistently lower than the average. The spatio-temporal annual streamflow volume patterns observed in this work can help to contextualize short-term trends and regional studies already available in the scientific literature as well as to provide a valid benchmark for further accurate quantitative analysis on annual streamflow volumes.
The impact of meltwater discharge from the Greenland ice sheet on the Atlantic nutrient supply to the northwest European shelf
Authors: Mathis Moritz , Mikolajewicz Uwe
Published: January 2020

Abstract. Projected future shoaling of the wintertime mixed layer in the northeast (NE) Atlantic has been shown to induce a regime shift in the main nutrient supply pathway from the Atlantic to the northwest European shelf (NWES) near the end of the 21st century. While reduced winter convection leads to a substantial decrease in the vertical nutrient supply and biological productivity in the open ocean, vertical mixing processes at the shelf break maintain a connection to the subpycnocline nutrient pool and thus productivity on the shelf. Here, we investigate how meltwater discharge from the Greenland ice sheet (GIS), not yet taken into account, impacts the mixed layer shoaling and the regime shift in terms of spatial distribution and temporal variability. To this end, we have downscaled sensitivity experiments by a global Earth system model for various GIS melting rates with a regionally coupled ocean–atmosphere climate system model. The model results indicate that increasing GIS meltwater discharge leads to a general intensification of the regime shift. Atlantic subpycnocline water masses mixed up at the shelf break become richer in nutrients and thus further limit the projected nutrient decline on the shelf. Moreover, the stronger vertical nutrient gradient through the pycnocline results in an enhanced interannual variability of on-shelf nutrient fluxes which, however, do not significantly increase variations in nutrient concentrations and primary production on the shelf. Due to the impact of the GIS meltwater discharge on the NE Atlantic mixed layer depth, the regime shift becomes initiated earlier in the century. The effect on the onset timing, though, is found to be strongly damped by the weakening of the Atlantic meridional overturning circulation. A GIS melting rate that is even 10 times higher than expected for emission scenario Representative Concentration Pathway (RCP) 8.5 would not lead to an onset of the regime shift until the 2070s.